From 6b4e5e9ce8569163ef4512024c0feb08f9bfeb3e Mon Sep 17 00:00:00 2001
From: Baivab Sarkar <baivabsarkar@gmail.com>
Date: Thu, 11 Jun 2026 11:13:27 +0530
Subject: [PATCH 1/4] fix: resolve blank page and timeout errors on large PDF
 exports

---
 desktop-app/resources/js/script.js | 92 ++++++++++++++++++------------
 script.js                          | 92 ++++++++++++++++++------------
 2 files changed, 110 insertions(+), 74 deletions(-)

diff --git a/desktop-app/resources/js/script.js b/desktop-app/resources/js/script.js
index 9f457d2a..4ddda0b6 100644
--- a/desktop-app/resources/js/script.js
+++ b/desktop-app/resources/js/script.js
@@ -8158,50 +8158,68 @@ document.addEventListener("DOMContentLoaded", function () {
       const contentWidth = pageWidth - (margin * 2);
       const captureScale = choosePdfCanvasScale(tempElement);
 
-      updatePdfProgress(progressState, 65, "Capturing document");
-      const canvas = await runPdfAbortable(progressState, html2canvas(tempElement, {
-        scale: captureScale,
-        useCORS: true,
-        allowTaint: false,
-        logging: false,
-        windowWidth: Math.max(PAGE_CONFIG.windowWidth, Math.ceil(tempElement.getBoundingClientRect().width)),
-        windowHeight: Math.ceil(tempElement.getBoundingClientRect().height)
-      }));
-      await waitForPdfFrame(progressState);
-      throwIfPdfExportAborted(progressState.signal);
+      const pageCount = pageBreakAnalysis.pageCount;
+      const pageHeightPx = pageBreakAnalysis.pageHeightPx;
+      const totalHeight = Math.ceil(tempElement.getBoundingClientRect().height);
+
+      const PAGES_PER_CHUNK = 8;
+      const chunkCount = Math.ceil(pageCount / PAGES_PER_CHUNK);
 
-      console.log(`[PDF DEBUG] canvas.width = ${canvas.width}, canvas.height = ${canvas.height}`);
-      console.log(`[PDF DEBUG] tempElement.offsetWidth = ${tempElement.offsetWidth}, rect.width = ${tempElement.getBoundingClientRect().width}`);
-      const scaleFactor = canvas.width / contentWidth;
-      console.log(`[PDF DEBUG] scaleFactor = ${scaleFactor}, PAGE_CONFIG.scale = ${PAGE_CONFIG.scale}, captureScale = ${captureScale}`);
-      const imgHeight = canvas.height / scaleFactor;
-      console.log(`[PDF DEBUG] imgHeight = ${imgHeight}, contentHeight = ${pageHeight - margin * 2}`);
-      // Introduce a 0.5mm tolerance to prevent rounding errors from creating a trailing blank page
-      const pagesCount = Math.ceil((imgHeight - 0.5) / (pageHeight - margin * 2));
-      console.log(`[PDF DEBUG] pagesCount = ${pagesCount}`);
-
-      updatePdfProgress(progressState, 76, "Rendering pages");
-      for (let page = 0; page < pagesCount; page++) {
+      logPdfExportDebug("Starting hybrid chunked capture loop. Total pages:", pageCount, "Chunks:", chunkCount);
+      updatePdfProgress(progressState, 65, "Rendering pages");
+
+      for (let c = 0; c < chunkCount; c++) {
         throwIfPdfExportAborted(progressState.signal);
-        const pageProgress = 76 + ((page + 1) / pagesCount) * 18;
-        updatePdfProgress(progressState, pageProgress, `Rendering page ${page + 1} of ${pagesCount}`);
+        
+        const startPage = c * PAGES_PER_CHUNK;
+        const endPage = Math.min((c + 1) * PAGES_PER_CHUNK, pageCount);
+        
+        const yStart = startPage * pageHeightPx;
+        const chunkHeight = Math.min(totalHeight - yStart, (endPage - startPage) * pageHeightPx);
+
+        const progressPercent = 65 + ((c + 1) / chunkCount) * 33;
+        updatePdfProgress(progressState, progressPercent, `Rendering page ${startPage + 1} to ${endPage} of ${pageCount}`);
 
-        if (page > 0) pdf.addPage();
+        console.log(`[PDF DEBUG] Rendering chunk ${c + 1}/${chunkCount}: yStart=${yStart}, chunkHeight=${chunkHeight}`);
+        
+        const chunkCanvas = await runPdfAbortable(progressState, html2canvas(tempElement, {
+          scale: captureScale,
+          useCORS: true,
+          allowTaint: false,
+          logging: false,
+          x: 0,
+          y: yStart,
+          width: tempElement.offsetWidth,
+          height: chunkHeight,
+          windowWidth: Math.max(PAGE_CONFIG.windowWidth, Math.ceil(tempElement.getBoundingClientRect().width)),
+          windowHeight: totalHeight,
+          scrollX: 0,
+          scrollY: 0
+        }));
+
+        const chunkPagesCount = endPage - startPage;
+        for (let p = 0; p < chunkPagesCount; p++) {
+          throwIfPdfExportAborted(progressState.signal);
+          const pageIndex = startPage + p;
+          
+          if (pageIndex > 0) pdf.addPage();
 
-        const sourceY = page * (pageHeight - margin * 2) * scaleFactor;
-        const sourceHeight = Math.min(canvas.height - sourceY, (pageHeight - margin * 2) * scaleFactor);
-        const destHeight = sourceHeight / scaleFactor;
+          const pageYInChunkCanvas = p * pageHeightPx * captureScale;
+          const pageHeightInChunkCanvas = Math.min(chunkCanvas.height - pageYInChunkCanvas, pageHeightPx * captureScale);
 
-        const pageCanvas = document.createElement('canvas');
-        pageCanvas.width = canvas.width;
-        pageCanvas.height = sourceHeight;
+          const pageCanvas = document.createElement('canvas');
+          pageCanvas.width = chunkCanvas.width;
+          pageCanvas.height = pageHeightInChunkCanvas;
 
-        const ctx = pageCanvas.getContext('2d');
-        ctx.drawImage(canvas, 0, sourceY, canvas.width, sourceHeight, 0, 0, canvas.width, sourceHeight);
+          const ctx = pageCanvas.getContext('2d');
+          ctx.drawImage(chunkCanvas, 0, pageYInChunkCanvas, chunkCanvas.width, pageHeightInChunkCanvas, 0, 0, chunkCanvas.width, pageHeightInChunkCanvas);
 
-        const imgData = pageCanvas.toDataURL('image/png');
-        pdf.addImage(imgData, 'PNG', margin, margin, contentWidth, destHeight);
-        await waitForPdfFrame(progressState);
+          const imgData = pageCanvas.toDataURL('image/jpeg', 0.95);
+          const destHeight = (pageHeightInChunkCanvas / captureScale) / (pageCanvas.width / contentWidth);
+          pdf.addImage(imgData, 'JPEG', margin, margin, contentWidth, destHeight);
+          
+          await waitForPdfFrame(progressState);
+        }
       }
 
       throwIfPdfExportAborted(progressState.signal);
diff --git a/script.js b/script.js
index 9f457d2a..4ddda0b6 100644
--- a/script.js
+++ b/script.js
@@ -8158,50 +8158,68 @@ document.addEventListener("DOMContentLoaded", function () {
       const contentWidth = pageWidth - (margin * 2);
       const captureScale = choosePdfCanvasScale(tempElement);
 
-      updatePdfProgress(progressState, 65, "Capturing document");
-      const canvas = await runPdfAbortable(progressState, html2canvas(tempElement, {
-        scale: captureScale,
-        useCORS: true,
-        allowTaint: false,
-        logging: false,
-        windowWidth: Math.max(PAGE_CONFIG.windowWidth, Math.ceil(tempElement.getBoundingClientRect().width)),
-        windowHeight: Math.ceil(tempElement.getBoundingClientRect().height)
-      }));
-      await waitForPdfFrame(progressState);
-      throwIfPdfExportAborted(progressState.signal);
+      const pageCount = pageBreakAnalysis.pageCount;
+      const pageHeightPx = pageBreakAnalysis.pageHeightPx;
+      const totalHeight = Math.ceil(tempElement.getBoundingClientRect().height);
+
+      const PAGES_PER_CHUNK = 8;
+      const chunkCount = Math.ceil(pageCount / PAGES_PER_CHUNK);
 
-      console.log(`[PDF DEBUG] canvas.width = ${canvas.width}, canvas.height = ${canvas.height}`);
-      console.log(`[PDF DEBUG] tempElement.offsetWidth = ${tempElement.offsetWidth}, rect.width = ${tempElement.getBoundingClientRect().width}`);
-      const scaleFactor = canvas.width / contentWidth;
-      console.log(`[PDF DEBUG] scaleFactor = ${scaleFactor}, PAGE_CONFIG.scale = ${PAGE_CONFIG.scale}, captureScale = ${captureScale}`);
-      const imgHeight = canvas.height / scaleFactor;
-      console.log(`[PDF DEBUG] imgHeight = ${imgHeight}, contentHeight = ${pageHeight - margin * 2}`);
-      // Introduce a 0.5mm tolerance to prevent rounding errors from creating a trailing blank page
-      const pagesCount = Math.ceil((imgHeight - 0.5) / (pageHeight - margin * 2));
-      console.log(`[PDF DEBUG] pagesCount = ${pagesCount}`);
-
-      updatePdfProgress(progressState, 76, "Rendering pages");
-      for (let page = 0; page < pagesCount; page++) {
+      logPdfExportDebug("Starting hybrid chunked capture loop. Total pages:", pageCount, "Chunks:", chunkCount);
+      updatePdfProgress(progressState, 65, "Rendering pages");
+
+      for (let c = 0; c < chunkCount; c++) {
         throwIfPdfExportAborted(progressState.signal);
-        const pageProgress = 76 + ((page + 1) / pagesCount) * 18;
-        updatePdfProgress(progressState, pageProgress, `Rendering page ${page + 1} of ${pagesCount}`);
+        
+        const startPage = c * PAGES_PER_CHUNK;
+        const endPage = Math.min((c + 1) * PAGES_PER_CHUNK, pageCount);
+        
+        const yStart = startPage * pageHeightPx;
+        const chunkHeight = Math.min(totalHeight - yStart, (endPage - startPage) * pageHeightPx);
+
+        const progressPercent = 65 + ((c + 1) / chunkCount) * 33;
+        updatePdfProgress(progressState, progressPercent, `Rendering page ${startPage + 1} to ${endPage} of ${pageCount}`);
 
-        if (page > 0) pdf.addPage();
+        console.log(`[PDF DEBUG] Rendering chunk ${c + 1}/${chunkCount}: yStart=${yStart}, chunkHeight=${chunkHeight}`);
+        
+        const chunkCanvas = await runPdfAbortable(progressState, html2canvas(tempElement, {
+          scale: captureScale,
+          useCORS: true,
+          allowTaint: false,
+          logging: false,
+          x: 0,
+          y: yStart,
+          width: tempElement.offsetWidth,
+          height: chunkHeight,
+          windowWidth: Math.max(PAGE_CONFIG.windowWidth, Math.ceil(tempElement.getBoundingClientRect().width)),
+          windowHeight: totalHeight,
+          scrollX: 0,
+          scrollY: 0
+        }));
+
+        const chunkPagesCount = endPage - startPage;
+        for (let p = 0; p < chunkPagesCount; p++) {
+          throwIfPdfExportAborted(progressState.signal);
+          const pageIndex = startPage + p;
+          
+          if (pageIndex > 0) pdf.addPage();
 
-        const sourceY = page * (pageHeight - margin * 2) * scaleFactor;
-        const sourceHeight = Math.min(canvas.height - sourceY, (pageHeight - margin * 2) * scaleFactor);
-        const destHeight = sourceHeight / scaleFactor;
+          const pageYInChunkCanvas = p * pageHeightPx * captureScale;
+          const pageHeightInChunkCanvas = Math.min(chunkCanvas.height - pageYInChunkCanvas, pageHeightPx * captureScale);
 
-        const pageCanvas = document.createElement('canvas');
-        pageCanvas.width = canvas.width;
-        pageCanvas.height = sourceHeight;
+          const pageCanvas = document.createElement('canvas');
+          pageCanvas.width = chunkCanvas.width;
+          pageCanvas.height = pageHeightInChunkCanvas;
 
-        const ctx = pageCanvas.getContext('2d');
-        ctx.drawImage(canvas, 0, sourceY, canvas.width, sourceHeight, 0, 0, canvas.width, sourceHeight);
+          const ctx = pageCanvas.getContext('2d');
+          ctx.drawImage(chunkCanvas, 0, pageYInChunkCanvas, chunkCanvas.width, pageHeightInChunkCanvas, 0, 0, chunkCanvas.width, pageHeightInChunkCanvas);
 
-        const imgData = pageCanvas.toDataURL('image/png');
-        pdf.addImage(imgData, 'PNG', margin, margin, contentWidth, destHeight);
-        await waitForPdfFrame(progressState);
+          const imgData = pageCanvas.toDataURL('image/jpeg', 0.95);
+          const destHeight = (pageHeightInChunkCanvas / captureScale) / (pageCanvas.width / contentWidth);
+          pdf.addImage(imgData, 'JPEG', margin, margin, contentWidth, destHeight);
+          
+          await waitForPdfFrame(progressState);
+        }
       }
 
       throwIfPdfExportAborted(progressState.signal);

From 8ca2cfc2e6d74872070840c673c1a36b09e9442e Mon Sep 17 00:00:00 2001
From: Baivab Sarkar <baivabsarkar@gmail.com>
Date: Thu, 11 Jun 2026 11:54:01 +0530
Subject: [PATCH 2/4] fix: resolve squished PDF layout and add native print
 dialog fallback for large documents

---
 desktop-app/resources/js/script.js |   79 +-
 desktop-app/resources/styles.css   | 7703 ++++++++++++++--------------
 script.js                          |   79 +-
 styles.css                         | 7703 ++++++++++++++--------------
 4 files changed, 7886 insertions(+), 7678 deletions(-)

diff --git a/desktop-app/resources/js/script.js b/desktop-app/resources/js/script.js
index 4ddda0b6..7cbfd9bd 100644
--- a/desktop-app/resources/js/script.js
+++ b/desktop-app/resources/js/script.js
@@ -7964,18 +7964,51 @@ document.addEventListener("DOMContentLoaded", function () {
     return Promise.all(promises);
   }
 
-  // ============================================
-  // End Oversized Graphics Scaling Functions
-  // ============================================
+  function showLargePdfExportDialog(onChoosePrint, onChooseCanvas) {
+    const dialogOverlay = document.createElement("div");
+    dialogOverlay.className = "reset-modal-overlay";
+    dialogOverlay.style.display = "flex";
+    dialogOverlay.setAttribute("role", "dialog");
+    dialogOverlay.setAttribute("aria-modal", "true");
+
+    dialogOverlay.innerHTML = `
+      <div class="reset-modal-box reset-modal-box--wide">
+        <p class="reset-modal-message" style="font-weight: 600; margin-bottom: 0.5rem; color: var(--text-color);">Large Document Detected</p>
+        <p style="font-size: 0.9rem; margin-bottom: 1.5rem; opacity: 0.85; line-height: 1.4; color: var(--text-color);">
+          This document is very large. Generating a canvas-based PDF can take a long time and might cause browser lagging. 
+          <br><br>
+          We recommend using the <strong>Browser Print Dialog</strong> (select 'Save as PDF' as the destination). It is instant, uses vector graphics for perfectly sharp text, and has zero document size limits.
+        </p>
+        <div class="reset-modal-actions" style="display: flex; gap: 10px; justify-content: flex-end; flex-wrap: wrap;">
+          <button class="reset-modal-btn reset-modal-cancel" id="large-pdf-cancel" style="border: 1px solid var(--border-color); background: none; color: var(--text-color);">Cancel</button>
+          <button class="reset-modal-btn" id="large-pdf-canvas" style="background-color: var(--button-bg); border: 1px solid var(--border-color); color: var(--text-color);">Use Canvas (Slow)</button>
+          <button class="reset-modal-btn" id="large-pdf-print" style="background-color: var(--accent-color); border: none; color: #ffffff; font-weight: 600;">Browser Print (Recommended)</button>
+        </div>
+      </div>
+    `;
 
-  exportPdf.addEventListener("click", async function (event) {
-    event.preventDefault();
-    logPdfExportDebug("PDF export button clicked!");
-    if (activePdfExport) {
-      logPdfExportDebug("PDF export already active, ignoring click");
-      return;
-    }
+    document.body.appendChild(dialogOverlay);
 
+    const cleanup = () => {
+      dialogOverlay.remove();
+    };
+
+    dialogOverlay.querySelector("#large-pdf-cancel").addEventListener("click", () => {
+      cleanup();
+    });
+
+    dialogOverlay.querySelector("#large-pdf-canvas").addEventListener("click", () => {
+      cleanup();
+      onChooseCanvas();
+    });
+
+    dialogOverlay.querySelector("#large-pdf-print").addEventListener("click", () => {
+      cleanup();
+      onChoosePrint();
+    });
+  }
+
+  async function startCanvasPdfExport() {
     const progressState = createPdfProgressState();
     activePdfExport = progressState;
     setPdfExportTriggersBusy(progressState, true);
@@ -8237,6 +8270,32 @@ document.addEventListener("DOMContentLoaded", function () {
     } finally {
       cleanupPdfExport(progressState);
     }
+  }
+
+  exportPdf.addEventListener("click", async function (event) {
+    event.preventDefault();
+    logPdfExportDebug("PDF export button clicked!");
+    if (activePdfExport) {
+      logPdfExportDebug("PDF export already active, ignoring click");
+      return;
+    }
+
+    const markdown = markdownEditor.value;
+    // Set a threshold of 30,000 characters for large documents
+    if (markdown.length > 30000) {
+      showLargePdfExportDialog(
+        () => {
+          // Choice: Browser Print
+          window.print();
+        },
+        () => {
+          // Choice: Canvas rendering
+          startCanvasPdfExport();
+        }
+      );
+    } else {
+      startCanvasPdfExport();
+    }
   });
 
   copyMarkdownButton.addEventListener("click", function () {
diff --git a/desktop-app/resources/styles.css b/desktop-app/resources/styles.css
index aafd5a8a..c0c8401f 100644
--- a/desktop-app/resources/styles.css
+++ b/desktop-app/resources/styles.css
@@ -1,3873 +1,3918 @@
-:root {
-  --bg-color: #ffffff;
-  --editor-bg: #f6f8fa;
-  --preview-bg: #ffffff; /* Preview background for light mode */
-  --text-color: #24292e;
-  --text-secondary: #57606a;
-  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
-  --color-danger-fg: #d73a49;
-  --preview-text-color: #24292e; /* Text color for preview in light mode */
-  --border-color: #e1e4e8;
-  --header-bg: #f6f8fa;
-  --button-bg: #f6f8fa;
-  --button-hover: #e1e4e8;
-  --button-active: #d1d5da;
-  --scrollbar-thumb: #c1c1c1;
-  --scrollbar-track: #f1f1f1;
-  --accent-color: #0366d6;
-  --table-bg: #ffffff; /* Table background for light mode */
-  --code-bg: #f6f8fa; /* Code block background for light mode */
-  --skeleton-bg: #e2e8f0;
-  --skeleton-glow: rgba(255, 255, 255, 0.65);
-
-  /* Find & Replace Panel custom properties (PERF-010 consolidated) */
-  --fr-bg: rgba(255, 255, 255, 0.95);
-  --fr-border: #d0d7de;
-  --fr-shadow: 0 8px 24px rgba(140, 149, 159, 0.2);
-  --fr-btn-active: #0969da;
-  --fr-btn-active-bg: #ddf4ff;
-  --fr-match-highlight: #ffdf5d;
-  --fr-match-active: #ff9b30;
-  --fr-match-text-color: #24292e;
-  --fr-match-active-text-color: #24292e;
-  --fr-error-bg: #ffebe9;
-  --fr-error-border: #ff8577;
-  --fr-text-danger: #cf222e;
-}
-
-[data-theme="dark"] {
-  --bg-color: #0d1117;
-  --editor-bg: #161b22;
-  --preview-bg: #0d1117; /* Preview background for dark mode */
-  --text-color: #c9d1d9;
-  --text-secondary: #8b949e;
-  --color-danger-fg: #f85149;
-  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
-  --border-color: #30363d;
-  --header-bg: #161b22;
-  --button-bg: #21262d;
-  --button-hover: #30363d;
-  --button-active: #3b434b;
-  --scrollbar-thumb: #484f58;
-  --scrollbar-track: #21262d;
-  --accent-color: #58a6ff;
-  --table-bg: #161b22; /* Table background for dark mode */
-  --code-bg: #161b22; /* Code block background for dark mode */
-  --skeleton-bg: #2d3139;
-  --skeleton-glow: rgba(255, 255, 255, 0.08);
-
-  /* Find & Replace Panel custom properties for dark mode */
-  --fr-bg: rgba(28, 33, 40, 0.98);
-  --fr-border: #444c56;
-  --fr-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
-  --fr-btn-active: #2f81f7;
-  --fr-btn-active-bg: rgba(56, 139, 253, 0.15);
-  --fr-match-highlight: rgba(187, 128, 9, 0.4);
-  --fr-match-active: #ad6200;
-  --fr-match-text-color: #c9d1d9;
-  --fr-match-active-text-color: #ffffff;
-  --fr-error-bg: rgba(248, 81, 73, 0.1);
-  --fr-error-border: rgba(248, 81, 73, 0.4);
-  --fr-text-danger: #ff7b72;
-}
-
-* {
-  box-sizing: border-box;
-  margin: 0;
-  padding: 0;
-}
-
-@media (min-width: 768px) {
-  html,
-  body {
-    height: 100%;
-    overflow: hidden;
-  }
-}
-
-body {
-  background-color: var(--bg-color);
-  color: var(--text-color);
-  /* PERF-021: Removed background-color transition to avoid full-viewport repaint on theme toggle */
-  transition: color 0.15s ease;
-  min-height: 100vh;
-  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
-}
-
-.app-header {
-  background-color: var(--header-bg);
-  border-bottom: 1px solid var(--border-color);
-  padding: 0.35rem 0.75rem;
-  transition: background-color 0.3s ease;
-  position: relative;
-  z-index: 100;
-  flex-shrink: 0;
-}
-
-.app-container {
-  height: 100vh;
-  display: flex;
-  flex-direction: column;
-  overflow: hidden;
-}
-
-.content-container {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-}
-
-.editor-pane, .preview-pane {
-  flex: 1;
-  padding: 20px;
-  overflow-y: auto;
-  position: relative;
-  /* PERF-025: Shortened transition and scoped to background-color only */
-  transition: background-color 0.15s ease;
-}
-
-.editor-pane {
-  background-color: var(--editor-bg);
-  border-right: 1px solid var(--border-color);
-  padding-right: 0px;
-  --line-number-gutter: 0px;
-}
-
-.preview-pane {
-  background-color: var(--preview-bg); /* Using the new variable for preview background */
-}
-
-/* Custom scrollbar */
-.editor-pane::-webkit-scrollbar,
-.preview-pane::-webkit-scrollbar,
-#markdown-editor::-webkit-scrollbar {
-  width: 8px;
-  height: 8px;
-}
-
-.editor-pane::-webkit-scrollbar-track,
-.preview-pane::-webkit-scrollbar-track,
-#markdown-editor::-webkit-scrollbar-track {
-  background: var(--scrollbar-track);
-}
-
-.editor-pane::-webkit-scrollbar-thumb,
-.preview-pane::-webkit-scrollbar-thumb,
-#markdown-editor::-webkit-scrollbar-thumb {
-  background: var(--scrollbar-thumb);
-  border-radius: 4px;
-}
-
-.editor-pane::-webkit-scrollbar-thumb:hover,
-.preview-pane::-webkit-scrollbar-thumb:hover,
-#markdown-editor::-webkit-scrollbar-thumb:hover {
-  background: var(--button-active);
-}
-
-#markdown-editor {
-  width: 100%;
-  height: 100%;
-  border: none;
-  background-color: transparent;
-  color: var(--text-color);
-  resize: none;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 14px;
-  line-height: 1.5;
-  padding: 10px;
-  padding-left: calc(10px + var(--line-number-gutter));
-  transition: background-color 0.3s ease, color 0.3s ease;
-  overflow-y: auto;
-  position: relative;
-  z-index: 3;
-}
-
-#markdown-editor:focus {
-  outline: none;
-}
-
-.preview-pane {
-  padding: 20px;
-}
-
-.markdown-body {
-  padding: 20px;
-  width: 100%;
-  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
-  color: var(--preview-text-color); /* Using specific text color for preview content */
-}
-
-.markdown-body a.reference-link {
-  font-size: 0.75em;
-  letter-spacing: -0.02em;
-  line-height: 1;
-  vertical-align: super;
-  position: relative;
-  top: 0.08em;
-}
-
-/* Style tables in light mode */
-.markdown-body table {
-  background-color: var(--table-bg);
-  border-color: var(--border-color);
-}
-
-.markdown-body table tr {
-  background-color: var(--table-bg);
-  border-top: 1px solid var(--border-color);
-}
-
-.markdown-body table tr:nth-child(2n) {
-  background-color: var(--bg-color);
-}
-
-/* Style code blocks in light mode */
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-/* ========================================
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-/* ========================================
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-.tab-close-btn:hover {
-  background-color: var(--button-active);
-  opacity: 1 !important;
-  color: var(--color-danger-fg, #d73a49);
-}
-
-.tab-new-btn {
-  display: flex;
-  align-items: center;
-  gap: 4px;
-  height: 24px;
-  padding: 0 8px;
-  border-radius: 5px;
-  background: none;
-  border: 1px solid var(--border-color);
-  color: var(--text-color);
-  cursor: pointer;
-  font-size: 12px;
-  flex-shrink: 0;
-  margin-left: 6px;
-  align-self: center;
-  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
-}
-
-.tab-new-btn:hover {
-  background-color: rgba(46, 160, 67, 0.1);
-  border-color: var(--accent-color, #2ea043);
-  color: var(--accent-color, #2ea043);
-}
-
-.tab-new-btn:active {
-  background-color: rgba(46, 160, 67, 0.2);
-}
-
-/* Drag-and-drop visual feedback */
-.tab-item.dragging {
-  opacity: 0.4;
-}
-
-.tab-item.drag-over {
-  border-left: 2px solid var(--accent-color);
-}
-
-/* Tab enter animation */
-@keyframes tabSlideIn {
-  from { opacity: 0; transform: translateY(4px); }
-  to   { opacity: 0.7; transform: translateY(0); }
-}
-
-.tab-item {
-  animation: tabSlideIn 0.12s ease forwards;
-}
-
-.tab-item.active {
-  animation: none;
-}
-
-/* Hide tab bar on very small screens — single-file use */
-@media (max-width: 480px) {
-  .tab-bar {
-    display: none;
-  }
-}
-
-/* ========================================
-   TAB OVERFLOW — Scroll Buttons & Fade Indicators
-   ======================================== */
-
-.tab-scroll-btn {
-  display: none;
-  align-items: center;
-  justify-content: center;
-  width: 24px;
-  height: 24px;
-  border-radius: 4px;
-  background: none;
-  border: 1px solid transparent;
-  color: var(--text-color);
-  cursor: pointer;
-  font-size: 14px;
-  flex-shrink: 0;
-  padding: 0;
-  transition: background-color 0.15s ease, border-color 0.15s ease, opacity 0.15s ease;
-  z-index: 2;
-  opacity: 0.6;
-}
-
-.tab-scroll-btn:hover {
-  background-color: var(--button-hover);
-  border-color: var(--border-color);
-  opacity: 1;
-}
-
-.tab-scroll-btn:active {
-  background-color: var(--button-active);
-}
-
-/* Show scroll buttons only when overflow exists */
-.tab-bar.has-overflow-left .tab-scroll-left,
-.tab-bar.has-overflow-right .tab-scroll-right {
-  display: flex;
-}
-
-/* Overflow fade indicators — subtle gradient at clipped edges */
-.tab-list::before,
-.tab-list::after {
-  content: '';
-  position: sticky;
-  top: 0;
-  bottom: 0;
-  width: 0;
-  flex-shrink: 0;
-  pointer-events: none;
-  z-index: 3;
-  transition: box-shadow 0.2s ease;
-}
-
-.tab-list::before {
-  left: 0;
-}
-
-.tab-list::after {
-  right: 0;
-}
-
-.tab-bar.has-overflow-left .tab-list::before {
-  box-shadow: 8px 0 12px -4px rgba(0, 0, 0, 0.12);
-}
-
-.tab-bar.has-overflow-right .tab-list::after {
-  box-shadow: -8px 0 12px -4px rgba(0, 0, 0, 0.12);
-}
-
-[data-theme="dark"] .tab-bar.has-overflow-left .tab-list::before {
-  box-shadow: 8px 0 12px -4px rgba(0, 0, 0, 0.35);
-}
-
-[data-theme="dark"] .tab-bar.has-overflow-right .tab-list::after {
-  box-shadow: -8px 0 12px -4px rgba(0, 0, 0, 0.35);
-}
-
-/* ========================================
-   THREE-DOT TAB MENU
-   ======================================== */
-
-.tab-menu-btn {
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  width: 22px;
-  height: 22px;
-  border-radius: 3px;
-  background: none;
-  border: none;
-  color: var(--text-color);
-  cursor: pointer;
-  padding: 0;
-  font-size: 14px;
-  font-weight: bold;
-  letter-spacing: 1px;
-  opacity: 0.65;
-  flex-shrink: 0;
-  transition: background-color 0.15s ease, opacity 0.15s ease;
-  position: relative;
-}
-
-/* Touch Hitbox Expansion for Tab Menu Button */
-.tab-menu-btn::before {
-  content: '';
-  position: absolute;
-  top: 50%;
-  left: 50%;
-  transform: translate(-50%, -50%);
-  width: 48px;
-  height: 48px;
-}
-
-/* Touch-optimized styling for coarser pointers (e.g., smartphones & tablets) */
-@media (pointer: coarse) {
-  .tab-bar {
-    height: 40px !important;
-  }
-  .tab-item {
-    height: 40px !important;
-    font-size: 14px !important;
-    padding: 0 10px 0 12px !important;
-    gap: 8px !important;
-  }
-  .tab-new-btn,
-  .tab-reset-btn {
-    height: 32px !important;
-    font-size: 14px !important;
-    padding: 0 12px !important;
-  }
-  .tab-scroll-btn {
-    width: 32px !important;
-    height: 32px !important;
-    font-size: 18px !important;
-  }
-  .tab-menu-btn {
-    width: 30px !important;
-    height: 30px !important;
-    font-size: 18px !important;
-  }
-  .tab-close-btn {
-    width: 20px !important;
-    height: 20px !important;
-    font-size: 13px !important;
-    opacity: 0.8 !important;
-  }
-}
-
-.tab-item:hover .tab-menu-btn,
-.tab-item.active .tab-menu-btn {
-  opacity: 0.65;
-}
-
-.tab-menu-btn:hover {
-  background-color: var(--button-active);
-  opacity: 1 !important;
-}
-
-.tab-menu-dropdown {
-  display: none;
-  position: fixed;
-  min-width: 130px;
-  background-color: var(--header-bg);
-  border: 1px solid var(--border-color);
-  border-radius: 6px;
-  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
-  z-index: 99999;
-  overflow: hidden;
-  flex-direction: column;
-}
-
-.tab-menu-dropdown.open {
-  display: flex;
-}
-
-.tab-menu-item {
-  display: flex;
-  align-items: center;
-  gap: 7px;
-  padding: 7px 12px;
-  background: none;
-  border: none;
-  color: var(--text-color);
-  font-size: 12px;
-  cursor: pointer;
-  text-align: left;
-  transition: background-color 0.12s ease;
-  white-space: nowrap;
-}
-
-.tab-menu-item:hover {
-  background-color: var(--button-hover);
-}
-
-.tab-menu-item-danger {
-  color: var(--color-danger-fg, #d73a49);
-}
-
-.tab-menu-item-danger:hover {
-  background-color: rgba(215, 58, 73, 0.1);
-}
-
-/* ========================================
-   RESET BUTTON
-   ======================================== */
-
-.tab-reset-btn {
-  display: flex;
-  align-items: center;
-  gap: 4px;
-  height: 24px;
-  padding: 0 8px;
-  border-radius: 5px;
-  background: none;
-  border: 1px solid var(--border-color);
-  color: var(--text-color);
-  cursor: pointer;
-  font-size: 12px;
-  flex-shrink: 0;
-  margin-left: 6px;
-  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
-}
-
-.tab-reset-btn:hover {
-  background-color: rgba(215, 58, 73, 0.1);
-  border-color: var(--color-danger-fg, #d73a49);
-  color: var(--color-danger-fg, #d73a49);
-}
-
-/* ========================================
-   RESET & RENAME CONFIRMATION MODALS
-   ======================================== */
-
-.reset-modal-overlay {
-  position: fixed;
-  inset: 0;
-  background: rgba(0, 0, 0, 0.45);
-  z-index: 2000;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-}
-
-.reset-modal-overlay.modal-overlay {
-  opacity: 0;
-  visibility: hidden;
-  transition: opacity 0.2s ease, visibility 0.2s ease;
-}
-
-.reset-modal-overlay.modal-overlay.is-visible {
-  opacity: 1;
-  visibility: visible;
-}
-
-.reset-modal-box {
-  background: var(--header-bg);
-  border: 1px solid var(--border-color);
-  border-radius: 10px;
-  padding: 24px 28px;
-  min-width: 280px;
-  max-width: 360px;
-  box-shadow: 0 8px 32px rgba(0,0,0,0.25);
-  display: flex;
-  flex-direction: column;
-  gap: 16px;
-}
-
-.modal-box {
-  max-height: min(85vh, 760px);
-  opacity: 0;
-  transform: translateY(8px);
-  transition: transform 0.2s ease, opacity 0.2s ease;
-}
-
-.reset-modal-overlay.modal-overlay.is-visible .modal-box {
-  opacity: 1;
-  transform: translateY(0);
-}
-
-.modal-header {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  gap: 12px;
-}
-
-.modal-header .reset-modal-message {
-  text-align: left;
-  flex: 1;
-}
-
-.modal-close-btn {
-  border: 1px solid var(--border-color);
-  background: var(--button-bg);
-  color: var(--text-color);
-  border-radius: 6px;
-  width: 28px;
-  height: 28px;
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  cursor: pointer;
-  transition: background-color 0.15s ease;
-}
-
-.modal-close-btn:hover {
-  background-color: var(--button-hover);
-}
-
-.modal-body {
-  display: flex;
-  flex-direction: column;
-  gap: 16px;
-  max-height: min(60vh, 520px);
-  overflow: auto;
-  padding-right: 4px;
-}
-
-.modal-section {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-}
-
-.modal-section-title {
-  margin: 0;
-  font-size: 0.95rem;
-  font-weight: 600;
-}
-
-.modal-list {
-  margin: 0;
-  padding-left: 1.1rem;
-  display: flex;
-  flex-direction: column;
-  gap: 6px;
-  font-size: 0.85rem;
-}
-
-.modal-list a {
-  color: var(--accent-color);
-  text-decoration: none;
-}
-
-.modal-list a:hover {
-  text-decoration: underline;
-}
-
-.modal-subtext {
-  margin: 0;
-  font-size: 12px;
-  color: var(--text-secondary, #57606a);
-  line-height: 1.4;
-}
-
-.find-replace-meta {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  gap: 12px;
-}
-
-.find-match-count {
-  font-size: 12px;
-  color: var(--text-secondary, #57606a);
-}
-
-.find-replace-nav {
-  display: inline-flex;
-  gap: 6px;
-}
-
-.find-nav-btn {
-  width: 28px;
-  height: 28px;
-  padding: 0;
-}
-
-.about-header {
-  display: flex;
-  align-items: center;
-  gap: 16px;
-  flex-wrap: wrap;
-}
-
-.about-logo {
-  width: 64px;
-  height: 64px;
-  border-radius: 12px;
-  border: 1px solid var(--border-color);
-  object-fit: cover;
-}
-
-.about-details {
-  display: flex;
-  flex-direction: column;
-  gap: 6px;
-}
-
-.about-title {
-  margin: 0;
-  font-size: 1.05rem;
-  font-weight: 600;
-}
-
-.about-description {
-  margin: 0;
-  font-size: 0.85rem;
-  color: var(--text-secondary, #57606a);
-}
-
-.about-meta {
-  margin: 0;
-  font-size: 0.78rem;
-  color: var(--text-secondary, #57606a);
-}
-
-.modal-body kbd {
-  padding: 2px 6px;
-  border-radius: 4px;
-  background-color: var(--button-bg);
-  border: 1px solid var(--border-color);
-  font-size: 0.75rem;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-}
-
-.reset-modal-box--wide {
-  width: min(92vw, 640px);
-  max-width: 640px;
-}
-
-.reset-modal-message {
-  margin: 0;
-  font-size: 14px;
-  color: var(--text-color);
-  font-weight: 500;
-  text-align: center;
-}
-
-.reset-modal-actions {
-  display: flex;
-  gap: 10px;
-  justify-content: flex-end;
-}
-
-.reset-modal-btn {
-  padding: 6px 16px;
-  border-radius: 6px;
-  border: 1px solid var(--border-color);
-  background: var(--button-bg);
-  color: var(--text-color);
-  font-size: 13px;
-  cursor: pointer;
-  transition: background-color 0.15s ease;
-}
-
-.reset-modal-btn:hover {
-  background-color: var(--button-hover);
-}
-
-.reset-modal-confirm {
-  background-color: var(--color-danger-fg, #d73a49);
-  border-color: var(--color-danger-fg, #d73a49);
-  color: #fff;
-}
-
-.reset-modal-confirm:hover {
-  background-color: #b02a37;
-  border-color: #b02a37;
-}
-
+:root {
+  --bg-color: #ffffff;
+  --editor-bg: #f6f8fa;
+  --preview-bg: #ffffff; /* Preview background for light mode */
+  --text-color: #24292e;
+  --text-secondary: #57606a;
+  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
+  --color-danger-fg: #d73a49;
+  --preview-text-color: #24292e; /* Text color for preview in light mode */
+  --border-color: #e1e4e8;
+  --header-bg: #f6f8fa;
+  --button-bg: #f6f8fa;
+  --button-hover: #e1e4e8;
+  --button-active: #d1d5da;
+  --scrollbar-thumb: #c1c1c1;
+  --scrollbar-track: #f1f1f1;
+  --accent-color: #0366d6;
+  --table-bg: #ffffff; /* Table background for light mode */
+  --code-bg: #f6f8fa; /* Code block background for light mode */
+  --skeleton-bg: #e2e8f0;
+  --skeleton-glow: rgba(255, 255, 255, 0.65);
+
+  /* Find & Replace Panel custom properties (PERF-010 consolidated) */
+  --fr-bg: rgba(255, 255, 255, 0.95);
+  --fr-border: #d0d7de;
+  --fr-shadow: 0 8px 24px rgba(140, 149, 159, 0.2);
+  --fr-btn-active: #0969da;
+  --fr-btn-active-bg: #ddf4ff;
+  --fr-match-highlight: #ffdf5d;
+  --fr-match-active: #ff9b30;
+  --fr-match-text-color: #24292e;
+  --fr-match-active-text-color: #24292e;
+  --fr-error-bg: #ffebe9;
+  --fr-error-border: #ff8577;
+  --fr-text-danger: #cf222e;
+}
+
+[data-theme="dark"] {
+  --bg-color: #0d1117;
+  --editor-bg: #161b22;
+  --preview-bg: #0d1117; /* Preview background for dark mode */
+  --text-color: #c9d1d9;
+  --text-secondary: #8b949e;
+  --color-danger-fg: #f85149;
+  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
+  --border-color: #30363d;
+  --header-bg: #161b22;
+  --button-bg: #21262d;
+  --button-hover: #30363d;
+  --button-active: #3b434b;
+  --scrollbar-thumb: #484f58;
+  --scrollbar-track: #21262d;
+  --accent-color: #58a6ff;
+  --table-bg: #161b22; /* Table background for dark mode */
+  --code-bg: #161b22; /* Code block background for dark mode */
+  --skeleton-bg: #2d3139;
+  --skeleton-glow: rgba(255, 255, 255, 0.08);
+
+  /* Find & Replace Panel custom properties for dark mode */
+  --fr-bg: rgba(28, 33, 40, 0.98);
+  --fr-border: #444c56;
+  --fr-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
+  --fr-btn-active: #2f81f7;
+  --fr-btn-active-bg: rgba(56, 139, 253, 0.15);
+  --fr-match-highlight: rgba(187, 128, 9, 0.4);
+  --fr-match-active: #ad6200;
+  --fr-match-text-color: #c9d1d9;
+  --fr-match-active-text-color: #ffffff;
+  --fr-error-bg: rgba(248, 81, 73, 0.1);
+  --fr-error-border: rgba(248, 81, 73, 0.4);
+  --fr-text-danger: #ff7b72;
+}
+
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+@media (min-width: 768px) {
+  html,
+  body {
+    height: 100%;
+    overflow: hidden;
+  }
+}
+
+body {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  /* PERF-021: Removed background-color transition to avoid full-viewport repaint on theme toggle */
+  transition: color 0.15s ease;
+  min-height: 100vh;
+  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
+}
+
+.app-header {
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  padding: 0.35rem 0.75rem;
+  transition: background-color 0.3s ease;
+  position: relative;
+  z-index: 100;
+  flex-shrink: 0;
+}
+
+.app-container {
+  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+}
+
+.editor-pane, .preview-pane {
+  flex: 1;
+  padding: 20px;
+  overflow-y: auto;
+  position: relative;
+  /* PERF-025: Shortened transition and scoped to background-color only */
+  transition: background-color 0.15s ease;
+}
+
+.editor-pane {
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  padding-right: 0px;
+  --line-number-gutter: 0px;
+}
+
+.preview-pane {
+  background-color: var(--preview-bg); /* Using the new variable for preview background */
+}
+
+/* Custom scrollbar */
+.editor-pane::-webkit-scrollbar,
+.preview-pane::-webkit-scrollbar,
+#markdown-editor::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-pane::-webkit-scrollbar-track,
+.preview-pane::-webkit-scrollbar-track,
+#markdown-editor::-webkit-scrollbar-track {
+  background: var(--scrollbar-track);
+}
+
+.editor-pane::-webkit-scrollbar-thumb,
+.preview-pane::-webkit-scrollbar-thumb,
+#markdown-editor::-webkit-scrollbar-thumb {
+  background: var(--scrollbar-thumb);
+  border-radius: 4px;
+}
+
+.editor-pane::-webkit-scrollbar-thumb:hover,
+.preview-pane::-webkit-scrollbar-thumb:hover,
+#markdown-editor::-webkit-scrollbar-thumb:hover {
+  background: var(--button-active);
+}
+
+#markdown-editor {
+  width: 100%;
+  height: 100%;
+  border: none;
+  background-color: transparent;
+  color: var(--text-color);
+  resize: none;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  padding: 10px;
+  padding-left: calc(10px + var(--line-number-gutter));
+  transition: background-color 0.3s ease, color 0.3s ease;
+  overflow-y: auto;
+  position: relative;
+  z-index: 3;
+}
+
+#markdown-editor:focus {
+  outline: none;
+}
+
+.preview-pane {
+  padding: 20px;
+}
+
+.markdown-body {
+  padding: 20px;
+  width: 100%;
+  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
+  color: var(--preview-text-color); /* Using specific text color for preview content */
+}
+
+.markdown-body a.reference-link {
+  font-size: 0.75em;
+  letter-spacing: -0.02em;
+  line-height: 1;
+  vertical-align: super;
+  position: relative;
+  top: 0.08em;
+}
+
+/* Style tables in light mode */
+.markdown-body table {
+  background-color: var(--table-bg);
+  border-color: var(--border-color);
+}
+
+.markdown-body table tr {
+  background-color: var(--table-bg);
+  border-top: 1px solid var(--border-color);
+}
+
+.markdown-body table tr:nth-child(2n) {
+  background-color: var(--bg-color);
+}
+
+/* Style code blocks in light mode */
+.markdown-body pre {
+  background-color: var(--code-bg);
+  border-radius: 6px;
+}
+
+.markdown-body code {
+  background-color: var(--code-bg);
+  border-radius: 3px;
+  padding: 0.2em 0.4em;
+}
+
+.markdown-body img.emoji-inline {
+  width: 1em;
+  height: 1em;
+  vertical-align: -0.1em;
+}
+
+.markdown-body ul,
+.markdown-body ol {
+  padding-left: 2em;
+  margin: 0.4em 0;
+}
+
+.markdown-body ul ul,
+.markdown-body ul ol,
+.markdown-body ol ul,
+.markdown-body ol ol {
+  margin-top: 0.2em;
+  margin-bottom: 0.2em;
+}
+
+.markdown-body ul.contains-task-list,
+.markdown-body li.task-list-item {
+  list-style: none;
+}
+
+.markdown-body ul.contains-task-list {
+  padding-left: 2em;
+}
+
+.markdown-body li.task-list-item input[type="checkbox"] {
+  margin: 0 0.5em 0.2em 0;
+  vertical-align: middle;
+  pointer-events: none;
+}
+
+.markdown-body li.task-list-item::marker {
+  content: "";
+}
+
+.markdown-body li:has(> input[type="checkbox"]) {
+  list-style: none;
+}
+
+.markdown-body li:has(> input[type="checkbox"])::marker {
+  content: "";
+}
+
+.markdown-body ul:has(> li > input[type="checkbox"]) {
+  list-style: none;
+  padding-left: 2em;
+}
+
+.markdown-body .footnotes {
+  margin-top: 1.5rem;
+  font-size: 0.9em;
+}
+
+.markdown-body .footnotes ol {
+  padding-left: 1.5em;
+}
+
+.markdown-body .footnotes ol > li::marker {
+  content: "[" counter(list-item) "] ";
+  font-weight: 600;
+}
+
+.markdown-body .footnotes li > p {
+  margin: 0.2em 0;
+}
+
+.markdown-body .footnote-ref a,
+.markdown-body .footnote-backref {
+  text-decoration: none;
+}
+
+.markdown-body .footnote-backref {
+  margin-left: 0.4em;
+}
+
+.markdown-body .markdown-alert {
+  padding: 0.5rem 1rem;
+  margin-bottom: 16px;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.markdown-body .markdown-alert > :last-child {
+  margin-bottom: 0;
+}
+
+.markdown-body .markdown-alert-title {
+  margin: 0 0 8px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.markdown-body .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.markdown-body .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.markdown-body .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.markdown-body .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.markdown-body .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.markdown-body .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.markdown-body .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--preview-text-color);
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-note {
+  color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+  border-left-color: #4493f8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-tip {
+  color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+  border-left-color: #3fb950;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-important {
+  color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+  border-left-color: #ab7df8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-warning {
+  color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+  border-left-color: #d29922;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-caution {
+  color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+  border-left-color: #f85149;
+}
+
+.toolbar {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.toolbar-group {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+}
+
+.toolbar-divider {
+  width: 1px;
+  height: 20px;
+  background-color: var(--border-color);
+  opacity: 0.7;
+}
+
+.tool-button {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 5px;
+  padding: 4px 8px;
+  font-size: 13px;
+  cursor: pointer;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  /* PERF-016: Specific transition properties instead of 'all' to avoid animating layout-triggering properties */
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tool-button:hover {
+  background-color: var(--button-hover);
+}
+
+.tool-button:active {
+  background-color: var(--button-active);
+}
+
+.tool-button:disabled,
+.tool-button[aria-disabled="true"] {
+  cursor: not-allowed;
+  opacity: 0.5;
+}
+
+.tool-button i {
+  font-size: 15px;
+}
+
+.tool-button.is-active,
+.tool-button.is-active:hover {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: rgba(3, 102, 214, 0.08);
+}
+
+.btn-text {
+  display: none;
+}
+
+.toolbar .tool-button {
+  height: 28px;
+  min-width: 28px;
+}
+
+.toolbar .tool-button.sync-active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+}
+
+.file-input {
+  display: none;
+}
+
+/* Drag overlay: full-screen drop target shown when user drags a file over the window */
+.drag-overlay {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 9999;
+  background-color: rgba(0, 0, 0, 0.45);
+  pointer-events: none;
+  align-items: center;
+  justify-content: center;
+}
+
+.drag-overlay.active {
+  display: flex;
+  pointer-events: auto;
+}
+
+.drag-overlay-inner {
+  border: 3px dashed var(--accent-color);
+  border-radius: 12px;
+  padding: 48px 64px;
+  text-align: center;
+  color: #ffffff;
+  background-color: rgba(3, 102, 214, 0.15);
+  animation: overlayPulse 1.4s ease-in-out infinite;
+}
+
+.drag-overlay-icon {
+  display: block;
+  font-size: 3rem;
+  margin-bottom: 12px;
+  color: var(--accent-color);
+}
+
+.drag-overlay-text {
+  font-size: 1.4rem;
+  font-weight: 600;
+  margin-bottom: 4px;
+}
+
+.drag-overlay-sub {
+  font-size: 0.85rem;
+  opacity: 0.75;
+  margin-bottom: 0;
+}
+
+@keyframes overlayPulse {
+  0%, 100% { transform: scale(1); }
+  50% { transform: scale(1.015); }
+}
+
+/* Editor drop hint: subtle text at bottom of editor pane, shown only when empty */
+.drop-hint {
+  position: absolute;
+  bottom: 14px;
+  left: 0;
+  right: 0;
+  text-align: center;
+  font-size: 0.75rem;
+  color: var(--text-color);
+  opacity: 0.35;
+  pointer-events: none;
+  user-select: none;
+  z-index: 3;
+}
+
+.editor-pane:has(#markdown-editor:not(:placeholder-shown)) .drop-hint {
+  display: none;
+}
+
+.line-numbers {
+  position: absolute;
+  top: 20px;
+  bottom: 20px;
+  left: 20px;
+  width: var(--line-number-gutter);
+  padding: 10px 8px 10px 0;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  text-align: right;
+  color: var(--text-secondary);
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  box-sizing: border-box;
+  overflow: hidden;
+  pointer-events: none;
+  user-select: none;
+  z-index: 2;
+  font-variant-numeric: tabular-nums;
+}
+
+.line-numbers .line-number {
+  display: block;
+  height: auto;
+}
+
+.editor-highlight-layer {
+  position: absolute;
+  inset: 20px 0 20px calc(20px + var(--line-number-gutter));
+  padding: 10px;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+  color: transparent;
+  pointer-events: none;
+  overflow: auto;
+  background-color: var(--editor-bg);
+  border-radius: 4px;
+  z-index: 1;
+}
+
+.editor-highlight-layer::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-thumb {
+  background: transparent;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+.find-highlight {
+  background-color: var(--fr-match-highlight, rgba(255, 223, 93, 0.4)) !important;
+  border-radius: 2px;
+  color: transparent !important;
+  padding: 0 !important;
+  margin: 0 !important;
+}
+
+.find-highlight.active {
+  background-color: var(--fr-match-active, #ff9b30) !important;
+  color: transparent !important;
+  padding: 0 !important;
+  margin: 0 !important;
+  outline: 1px solid var(--accent-color, #0366d6) !important;
+  outline-offset: -1px;
+}
+
+.preview-find-highlight {
+  background-color: var(--fr-match-highlight, rgba(255, 223, 93, 0.4)) !important;
+  color: var(--fr-match-text-color, inherit) !important;
+  border-radius: 2px;
+  padding: 0 1px !important;
+  margin: 0 !important;
+}
+
+.preview-find-highlight.active {
+  background-color: var(--fr-match-active, #ff9b30) !important;
+  color: var(--fr-match-active-text-color, inherit) !important;
+  outline: 1px solid var(--accent-color, #0366d6) !important;
+  outline-offset: -1px;
+}
+
+/* Dropdown improvements */
+.dropdown-menu {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+}
+
+.dropdown-item {
+  color: var(--text-color);
+}
+
+.dropdown-item:hover, .dropdown-item:focus {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+/* Markdown formatting toolbar */
+.markdown-format-toolbar {
+  display: flex;
+  align-items: center;
+  height: 34px;
+  padding: 0 6px;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  overflow-x: auto;
+  overflow-y: hidden;
+  flex-shrink: 0;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.markdown-format-toolbar::-webkit-scrollbar {
+  display: none;
+}
+
+.markdown-toolbar-group {
+  display: flex;
+  align-items: center;
+  gap: 2px;
+  height: 100%;
+  padding: 0 6px;
+  border-right: 1px solid var(--border-color);
+  flex-shrink: 0;
+}
+
+.markdown-toolbar-group:first-child {
+  padding-left: 0;
+}
+
+.markdown-toolbar-group:last-child {
+  border-right: none;
+  padding-right: 0;
+}
+
+.markdown-tool-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 26px;
+  height: 26px;
+  border: 1px solid transparent;
+  border-radius: 4px;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 14px;
+  line-height: 1;
+  padding: 0;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.markdown-tool-btn:hover,
+.markdown-tool-btn:focus-visible {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+}
+
+.markdown-tool-btn:active {
+  background-color: var(--button-active);
+}
+
+.markdown-tool-btn:disabled,
+.markdown-tool-btn.disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+  pointer-events: none;
+}
+
+.markdown-tool-btn i {
+  font-size: 15px;
+}
+
+.markdown-tool-btn[data-md-action="reference"] i::before {
+  content: "[ ]";
+  font-style: normal;
+  font-size: 12px;
+  letter-spacing: -0.12em;
+}
+
+.markdown-tool-btn.text-tool {
+  width: auto;
+  min-width: 26px;
+  padding: 0 5px;
+  font-weight: 600;
+  font-family: Georgia, "Times New Roman", serif;
+}
+
+.heading-group .markdown-tool-btn {
+  min-width: 30px;
+}
+
+
+
+/* Loading indicators */
+.loading {
+  opacity: 0.6;
+  pointer-events: none;
+}
+
+/* Focus outline for accessibility */
+button:focus, 
+a:focus {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+/* Animation for copied message */
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+/* Tooltip styles */
+.tooltip {
+  position: absolute;
+  background: var(--button-bg);
+  border: 1px solid var(--border-color);
+  padding: 5px 8px;
+  border-radius: 4px;
+  font-size: 12px;
+  z-index: 1000;
+  animation: fadeIn 0.2s ease;
+}
+
+/* Styles for GitHub markdown preview light mode */
+.markdown-body {
+  color-scheme: light;
+  --color-prettylights-syntax-comment: #6a737d;
+  --color-prettylights-syntax-constant: #005cc5;
+  --color-prettylights-syntax-entity: #6f42c1;
+  --color-prettylights-syntax-storage-modifier-import: #24292e;
+  --color-prettylights-syntax-entity-tag: #22863a;
+  --color-prettylights-syntax-keyword: #cf222e;
+  --color-prettylights-syntax-string: #032f62;
+  --color-prettylights-syntax-variable: #e36209;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #b31d28;
+  --color-prettylights-syntax-invalid-illegal-text: #fafbfc;
+  --color-prettylights-syntax-invalid-illegal-bg: #b31d28;
+  --color-prettylights-syntax-carriage-return-text: #fafbfc;
+  --color-prettylights-syntax-carriage-return-bg: #d73a49;
+  --color-prettylights-syntax-string-regexp: #22863a;
+  --color-prettylights-syntax-markup-list: #735c0f;
+  --color-prettylights-syntax-markup-heading: #005cc5;
+  --color-prettylights-syntax-markup-italic: #24292e;
+  --color-prettylights-syntax-markup-bold: #24292e;
+  --color-prettylights-syntax-markup-deleted-text: #b31d28;
+  --color-prettylights-syntax-markup-deleted-bg: #ffeef0;
+  --color-prettylights-syntax-markup-inserted-text: #22863a;
+  --color-prettylights-syntax-markup-inserted-bg: #f0fff4;
+  --color-prettylights-syntax-markup-changed-text: #e36209;
+  --color-prettylights-syntax-markup-changed-bg: #ffebda;
+  --color-prettylights-syntax-markup-ignored-text: #f6f8fa;
+  --color-prettylights-syntax-markup-ignored-bg: #005cc5;
+  --color-prettylights-syntax-meta-diff-range: #6f42c1;
+  --color-prettylights-syntax-brackethighlighter-angle: #586069;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #e1e4e8;
+  --color-prettylights-syntax-constant-other-reference-link: #032f62;
+  --color-fg-default: #24292e;
+  --color-fg-muted: #586069;
+  --color-fg-subtle: #6a737d;
+  --color-canvas-default: #ffffff;
+  --color-canvas-subtle: #f6f8fa;
+  --color-border-default: #e1e4e8;
+  --color-border-muted: #eaecef;
+  --color-neutral-muted: rgba(175,184,193,0.2);
+  --color-accent-fg: #0366d6;
+  --color-accent-emphasis: #0366d6;
+  --color-attention-subtle: #fff5b1;
+  --color-danger-fg: #d73a49;
+}
+
+/* Styles for GitHub markdown preview dark mode */
+[data-theme="dark"] .markdown-body {
+  color-scheme: dark;
+  --color-prettylights-syntax-comment: #8b949e;
+  --color-prettylights-syntax-constant: #79c0ff;
+  --color-prettylights-syntax-entity: #d2a8ff;
+  --color-prettylights-syntax-storage-modifier-import: #c9d1d9;
+  --color-prettylights-syntax-entity-tag: #7ee787;
+  --color-prettylights-syntax-keyword: #ff7b72;
+  --color-prettylights-syntax-string: #a5d6ff;
+  --color-prettylights-syntax-variable: #ffa657;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #f85149;
+  --color-prettylights-syntax-invalid-illegal-text: #f0f6fc;
+  --color-prettylights-syntax-invalid-illegal-bg: #8e1519;
+  --color-prettylights-syntax-carriage-return-text: #f0f6fc;
+  --color-prettylights-syntax-carriage-return-bg: #b62324;
+  --color-prettylights-syntax-string-regexp: #7ee787;
+  --color-prettylights-syntax-markup-list: #f2cc60;
+  --color-prettylights-syntax-markup-heading: #1f6feb;
+  --color-prettylights-syntax-markup-italic: #c9d1d9;
+  --color-prettylights-syntax-markup-bold: #c9d1d9;
+  --color-prettylights-syntax-markup-deleted-text: #ffdcd7;
+  --color-prettylights-syntax-markup-deleted-bg: #67060c;
+  --color-prettylights-syntax-markup-inserted-text: #aff5b4;
+  --color-prettylights-syntax-markup-inserted-bg: #033a16;
+  --color-prettylights-syntax-markup-changed-text: #ffdfb6;
+  --color-prettylights-syntax-markup-changed-bg: #5a1e02;
+  --color-prettylights-syntax-markup-ignored-text: #c9d1d9;
+  --color-prettylights-syntax-markup-ignored-bg: #1158c7;
+  --color-prettylights-syntax-meta-diff-range: #d2a8ff;
+  --color-prettylights-syntax-brackethighlighter-angle: #8b949e;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #484f58;
+  --color-prettylights-syntax-constant-other-reference-link: #a5d6ff;
+  --color-fg-default: #c9d1d9;
+  --color-fg-muted: #8b949e;
+  --color-fg-subtle: #484f58;
+  --color-canvas-default: #0d1117;
+  --color-canvas-subtle: #161b22;
+  --color-border-default: #30363d;
+  --color-border-muted: #21262d;
+  --color-neutral-muted: rgba(110,118,129,0.4);
+  --color-accent-fg: #58a6ff;
+  --color-accent-emphasis: #1f6feb;
+  --color-attention-subtle: rgba(187,128,9,0.15);
+  --color-danger-fg: #f85149;
+}
+
+/* Override specific styles for dark mode tables and code */
+[data-theme="dark"] .markdown-body table tr {
+  background-color: var(--table-bg);
+}
+
+[data-theme="dark"] .markdown-body table tr:nth-child(2n) {
+  background-color: #1c2128; /* Slightly lighter than base dark background */
+}
+
+[data-theme="dark"] .markdown-body pre {
+  background-color: var(--code-bg);
+}
+
+[data-theme="dark"] .markdown-body code {
+  background-color: var(--code-bg);
+}
+
+/* Syntax Highlighting Mapping to GitHub Variables */
+.hljs {
+  color: var(--color-fg-default);
+}
+.hljs-doctag,
+.hljs-keyword,
+.hljs-meta .hljs-keyword,
+.hljs-template-tag,
+.hljs-template-variable,
+.hljs-type,
+.hljs-variable.language_ {
+  color: var(--color-prettylights-syntax-keyword);
+}
+.hljs-title,
+.hljs-title.class_,
+.hljs-title.class_.inherited__,
+.hljs-title.function_ {
+  color: var(--color-prettylights-syntax-entity);
+}
+.hljs-attr,
+.hljs-attribute,
+.hljs-literal,
+.hljs-meta,
+.hljs-number,
+.hljs-operator,
+.hljs-variable,
+.hljs-selector-attr,
+.hljs-selector-class,
+.hljs-selector-id {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-regexp,
+.hljs-string,
+.hljs-meta .hljs-string {
+  color: var(--color-prettylights-syntax-string);
+}
+.hljs-built_in,
+.hljs-symbol {
+  color: var(--color-prettylights-syntax-variable);
+}
+.hljs-comment,
+.hljs-code,
+.hljs-formula {
+  color: var(--color-prettylights-syntax-comment);
+}
+.hljs-name,
+.hljs-quote,
+.hljs-selector-tag,
+.hljs-selector-pseudo {
+  color: var(--color-prettylights-syntax-entity-tag);
+}
+.hljs-subst {
+  color: var(--color-fg-default);
+}
+.hljs-section {
+  color: var(--color-prettylights-syntax-markup-heading);
+  font-weight: bold;
+}
+.hljs-bullet {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-emphasis {
+  color: var(--color-fg-default);
+  font-style: italic;
+}
+.hljs-strong {
+  color: var(--color-fg-default);
+  font-weight: bold;
+}
+.hljs-addition {
+  color: var(--color-prettylights-syntax-markup-inserted-text);
+  background-color: var(--color-prettylights-syntax-markup-inserted-bg);
+}
+.hljs-deletion {
+  color: var(--color-prettylights-syntax-markup-deleted-text);
+  background-color: var(--color-prettylights-syntax-markup-deleted-bg);
+}
+
+.stats-container {
+  font-size: 0.8rem;
+  color: var(--text-color);
+}
+
+.stat-item {
+  align-items: center;
+}
+
+.stat-item i {
+  font-size: 0.9rem;
+  opacity: 0.8;
+}
+
+#importDropdown,
+#exportDropdown,
+#languageDropdown {
+  font-size: 0.8rem;
+}
+
+#importDropdown i,
+#exportDropdown i,
+#languageDropdown i {
+  font-size: 0.9rem;
+}
+
+/* Ensure desktop dropdown menu options match the stats-container font size */
+[aria-labelledby="importDropdown"] .dropdown-item,
+[aria-labelledby="exportDropdown"] .dropdown-item,
+[aria-labelledby="languageDropdown"] .dropdown-item {
+  font-size: 0.8rem;
+}
+
+/* Ensure mobile menu import, export, and language dropdown triggers/options match the mobile stats-container font size */
+#mobile-import-button,
+#mobile-import-github-button,
+#mobile-export-md,
+#mobile-export-html,
+#mobile-export-pdf,
+#mobileLanguageDropdown {
+  font-size: 0.9rem !important;
+}
+
+[aria-labelledby="mobileLanguageDropdown"] .dropdown-item {
+  font-size: 0.9rem;
+}
+
+.editor-pane {
+  overflow: hidden;
+}
+
+/* Mobile Menu Styles */
+.mobile-menu {
+  display: none;
+  position: relative;
+  z-index: 1001;
+}
+
+
+
+/* slide‑in panel */
+.mobile-menu-panel {
+  position: fixed;
+  top: 0;
+  right: -300px;
+  width: 280px;
+  height: 100vh;
+  background-color: var(--bg-color);
+  box-shadow: -2px 0 10px rgba(0, 0, 0, 0.2);
+  transition: right 0.3s ease;
+  overflow-y: auto;
+  padding: 1rem;
+  display: flex;
+  flex-direction: column;
+  z-index: 1002;
+}
+
+.mobile-menu-panel.active {
+  right: 0;
+}
+
+/* translucent overlay behind panel */
+.mobile-menu-overlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100vh;
+  background-color: rgba(0, 0, 0, 0.5);
+  opacity: 0;
+  visibility: hidden;
+  pointer-events: none;
+  transition: opacity 0.3s ease, visibility 0.3s ease;
+  z-index: 1000;
+}
+
+.mobile-menu-overlay.active {
+  opacity: 1;
+  visibility: visible;
+  pointer-events: auto;
+}
+
+/* header inside mobile menu */
+.mobile-menu-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 1rem;
+}
+
+.mobile-menu-header h5 {
+  margin: 0;
+  font-size: 1.25rem;
+  color: var(--text-color);
+}
+
+/* stats section in mobile menu */
+.mobile-stats-container {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+  margin-bottom: 1rem;
+}
+
+.mobile-stats-container .stat-item {
+  font-size: 0.9rem;
+  color: var(--text-color);
+  display: flex;
+  align-items: center;
+}
+
+.mobile-stats-container .stat-item i {
+  margin-right: 0.5em;
+  opacity: 0.8;
+}
+
+/* menu buttons list */
+.mobile-menu-items {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  flex-grow: 1;
+}
+
+/* each menu item */
+.mobile-menu-item {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 6px;
+  padding: 0.6rem 1rem;
+  font-size: 1rem;
+  text-align: left;
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  transition: background-color 0.2s ease;
+  cursor: pointer;
+}
+
+.mobile-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-menu-item:active {
+  background-color: var(--button-active);
+}
+
+/* close button override */
+#close-mobile-menu.tool-button {
+  padding: 0.25rem 0.5rem;
+  font-size: 1rem;
+}
+
+/* Mobile document tabs section */
+.mobile-tabs-section {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-tabs-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 0.5rem;
+}
+
+.mobile-tabs-label {
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--text-color);
+  opacity: 0.8;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+.mobile-new-tab-btn {
+  background: none;
+  border: 1px solid var(--border-color);
+  border-radius: 4px;
+  color: var(--text-color);
+  padding: 2px 7px;
+  font-size: 0.9rem;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.15s ease;
+}
+
+.mobile-new-tab-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-list {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  max-height: 180px;
+  overflow-y: auto;
+}
+
+.mobile-tab-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  padding: 0.45rem 0.75rem;
+  font-size: 0.9rem;
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+  gap: 0.5rem;
+}
+
+.mobile-tab-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-item.active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: var(--bg-color);
+}
+
+.mobile-tab-title {
+  flex: 1;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  min-width: 0;
+}
+
+.mobile-tab-item .tab-menu-btn {
+  opacity: 0.6;
+}
+
+.mobile-tab-item:hover .tab-menu-btn,
+.mobile-tab-item.active .tab-menu-btn {
+  opacity: 0.8;
+}
+
+#mobile-tab-reset-btn {
+  margin-left: 0;
+  height: auto;
+  padding: 0.45rem 0.75rem;
+  justify-content: center;
+  font-size: 0.9rem;
+}
+
+/* ==========================================
+   NAVBAR RESPONSIVE BREAKPOINTS
+   >= 1080px : full desktop navbar
+   <  1080px : mobile hamburger + stacked panes
+   ========================================== */
+
+/* Mobile / tablet (< 1080px): switch to hamburger, stack panes */
+@media (max-width: 1079px) {
+  /* Override Bootstrap d-md-flex / d-md-none so the breakpoint is 1080px */
+  .stats-container,
+  .toolbar {
+    display: none !important;
+  }
+
+  /* Expand touch target sizes to meet WCAG mobile guidelines */
+  .markdown-tool-btn {
+    width: 36px !important;
+    height: 36px !important;
+    font-size: 16px !important;
+  }
+  .markdown-format-toolbar {
+    height: 44px !important;
+  }
+  .tab-close-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+  .tab-menu-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+
+  .mobile-menu {
+    display: block !important;
+  }
+
+  /* Stack editor and preview vertically */
+  .content-container {
+    flex-direction: column;
+  }
+
+  .editor-pane,
+  .preview-pane {
+    flex: none;
+    height: 50%;
+    border-right: none;
+  }
+
+  .editor-pane {
+    border-bottom: 1px solid var(--border-color);
+  }
+
+  /* Hide drag-resize divider (touch devices don't use it) */
+  .resize-divider {
+    display: none;
+  }
+
+  /* Single-pane view modes: occupy full height */
+  .content-container.view-editor-only .editor-pane,
+  .content-container.view-preview-only .preview-pane {
+    height: 100%;
+  }
+
+  .content-container.view-split .editor-pane,
+  .content-container.view-split .preview-pane {
+    height: 50%;
+  }
+}
+
+.github-link {
+  color: var(--text-color);
+  text-decoration: none;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: transform 0.2s ease, color 0.2s ease;
+  margin-right: 2rem;
+}
+
+.github-link:hover {
+  color: var(--accent-color);
+  transform: scale(1.1);
+}
+
+.github-link i {
+  font-size: 1.25rem;
+}
+
+/* ========================================
+   HEADER LAYOUT
+   ======================================== */
+.header-container {
+  position: relative;
+  min-height: 30px;
+}
+
+.app-header h1 {
+  font-size: 1.05rem;
+  line-height: 1.1;
+}
+
+.header-left {
+  flex: 1 0 auto;
+  justify-content: flex-start;
+  white-space: nowrap;
+}
+
+.header-right {
+  flex: 1 0 auto;
+  justify-content: flex-end;
+  white-space: nowrap;
+}
+
+/* Pane View States */
+.content-container.view-editor-only .preview-pane {
+  display: none;
+}
+
+.content-container.view-editor-only .editor-pane {
+  flex: 1;
+  border-right: none;
+}
+
+.content-container.view-preview-only .editor-pane {
+  display: none;
+}
+
+.content-container.view-preview-only .preview-pane {
+  flex: 1;
+}
+
+.content-container.view-split .editor-pane,
+.content-container.view-split .preview-pane {
+  flex: 1;
+}
+
+/* Compact desktop (< 1280px): compact toolbar */
+@media (max-width: 1280px) {
+  /* Compact toolbar at medium widths */
+  .toolbar {
+    gap: 4px;
+  }
+}
+
+
+
+/* ========================================
+   RESIZE DIVIDER - Story 1.3
+   ======================================== */
+
+.resize-divider {
+  width: 8px;
+  background-color: transparent;
+  cursor: col-resize;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+  position: relative;
+  z-index: 10;
+  transition: background-color 0.2s ease;
+}
+
+.resize-divider:hover {
+  background-color: var(--button-hover);
+}
+
+.resize-divider.dragging {
+  background-color: var(--accent-color);
+}
+
+.resize-divider-handle {
+  width: 2px;
+  height: 40px;
+  background-color: var(--border-color);
+  border-radius: 2px;
+  transition: background-color 0.2s ease, width 0.2s ease;
+}
+
+.resize-divider:hover .resize-divider-handle,
+.resize-divider.dragging .resize-divider-handle {
+  background-color: var(--accent-color);
+  width: 3px;
+}
+
+/* Hide divider in single-pane modes */
+.content-container.view-editor-only .resize-divider,
+.content-container.view-preview-only .resize-divider {
+  display: none;
+}
+
+
+
+/* Prevent text selection during drag */
+.resizing {
+  user-select: none;
+  cursor: col-resize !important;
+}
+
+.resizing * {
+  cursor: col-resize !important;
+}
+
+.resizing #markdown-preview,
+.resizing #markdown-editor,
+.resizing .line-numbers {
+  pointer-events: none !important;
+}
+
+/* ========================================
+   MOBILE VIEW MODE CONTROLS - Story 1.4
+   ======================================== */
+
+.mobile-view-mode-group {
+  display: flex;
+  gap: 0;
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-view-mode-btn {
+  flex: 1;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  padding: 8px 12px;
+  font-size: 14px;
+  cursor: pointer;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  transition: all 0.2s ease;
+}
+
+.mobile-view-mode-btn:first-child {
+  border-radius: 6px 0 0 6px;
+}
+
+.mobile-view-mode-btn:last-child {
+  border-radius: 0 6px 6px 0;
+}
+
+.mobile-view-mode-btn:not(:last-child) {
+  border-right: none;
+}
+
+.mobile-view-mode-btn:hover,
+.mobile-view-mode-btn:active {
+  background-color: var(--button-hover);
+}
+
+.mobile-view-mode-btn.active {
+  background-color: var(--button-bg);
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  border-width: 2px;
+  padding: 7px 11px;
+}
+
+.mobile-view-mode-btn.active:not(:last-child) {
+  border-right: 2px solid var(--accent-color);
+}
+
+.mobile-view-mode-btn i {
+  font-size: 18px;
+}
+
+.mobile-view-mode-btn span {
+  font-size: 12px;
+}
+
+/* ========================================
+   RESPONSIVE VIEW MODE FIXES - Story 1.5
+   ======================================== */
+
+
+
+/* ========================================
+   PDF EXPORT TABLE FIX - Rowspan/Colspan
+   ======================================== */
+
+/* Fix for html2canvas not properly rendering rowspan/colspan cells.
+   Apply backgrounds to cells instead of rows to prevent row backgrounds
+   from painting over rowspan cells during canvas capture. */
+.pdf-export table tr {
+  background-color: transparent !important;
+}
+
+.pdf-export table th,
+.pdf-export table td {
+  background-color: var(--table-bg, #ffffff);
+  position: relative;
+}
+
+.pdf-export table tr:nth-child(2n) th,
+.pdf-export table tr:nth-child(2n) td {
+  background-color: var(--bg-color, #f6f8fa);
+}
+
+/* Ensure rowspan cells render correctly */
+.pdf-export table th[rowspan],
+.pdf-export table td[rowspan] {
+  vertical-align: middle;
+  background-color: var(--table-bg, #ffffff) !important;
+}
+
+/* Ensure colspan cells render correctly */
+.pdf-export table th[colspan],
+.pdf-export table td[colspan] {
+  text-align: center;
+}
+
+/* Dark mode PDF export table fix */
+[data-theme="dark"] .pdf-export table th,
+[data-theme="dark"] .pdf-export table td {
+  background-color: var(--table-bg, #161b22);
+}
+
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) th,
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) td {
+  background-color: #1c2128;
+}
+
+[data-theme="dark"] .pdf-export table th[rowspan],
+[data-theme="dark"] .pdf-export table td[rowspan] {
+  background-color: var(--table-bg, #161b22) !important;
+}
+
+/* ========================================
+   MERMAID DIAGRAM TOOLBAR
+   ======================================== */
+
+.mermaid-container {
+  position: relative;
+}
+
+.mermaid-toolbar {
+  position: absolute;
+  top: 8px;
+  right: 8px;
+  display: flex;
+  gap: 4px;
+  opacity: 0;
+  transition: opacity 0.2s ease;
+  z-index: 10;
+}
+
+.mermaid-container:hover .mermaid-toolbar {
+  opacity: 1;
+}
+
+.mermaid-toolbar-btn {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 4px;
+  padding: 4px 7px;
+  font-size: 13px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  gap: 3px;
+  transition: background-color 0.2s ease, color 0.2s ease;
+  white-space: nowrap;
+}
+
+.mermaid-toolbar-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--accent-color);
+}
+
+.mermaid-toolbar-btn:active {
+  background-color: var(--button-active);
+}
+
+.mermaid-toolbar-btn i {
+  font-size: 14px;
+}
+
+/* ========================================
+   MERMAID ZOOM MODAL
+   ======================================== */
+
+#mermaid-zoom-modal {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 2000;
+  background-color: rgba(0, 0, 0, 0.75);
+  align-items: center;
+  justify-content: center;
+}
+
+#mermaid-zoom-modal.active {
+  display: flex;
+}
+
+.mermaid-modal-content {
+  background-color: var(--bg-color);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  padding: 16px;
+  width: 85vw;
+  height: 85vh;
+  max-width: 85vw;
+  max-height: 85vh;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+@media (max-width: 576px) {
+  .mermaid-modal-content {
+    width: 95vw;
+    height: 90vh;
+    max-width: 95vw;
+    max-height: 90vh;
+    padding: 10px;
+  }
+}
+
+.mermaid-modal-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.mermaid-modal-header span {
+  font-weight: 600;
+  font-size: 15px;
+  color: var(--text-color);
+}
+
+.mermaid-modal-close {
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 1.2rem;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.2s ease;
+}
+
+.mermaid-modal-close:hover {
+  background-color: var(--button-hover);
+}
+
+.mermaid-modal-diagram {
+  overflow: auto;
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 200px;
+  cursor: grab;
+}
+
+.mermaid-modal-diagram.dragging {
+  cursor: grabbing;
+}
+
+.mermaid-modal-diagram svg {
+  transform-origin: center;
+  transition: transform 0.1s ease;
+  max-width: none;
+}
+
+.mermaid-modal-controls {
+  display: flex;
+  justify-content: center;
+  gap: 8px;
+  flex-wrap: wrap;
+}
+
+.mermaid-modal-controls .mermaid-toolbar-btn {
+  opacity: 1;
+}
+
+/* ========================================
+   DOCUMENT TABS & SESSION MANAGEMENT
+   ======================================== */
+
+.tab-bar {
+  display: flex;
+  align-items: center;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  height: 32px;
+  overflow: visible;  /* ← was: overflow: hidden */
+  flex-shrink: 0;
+  padding: 0 4px;
+  gap: 0;
+  user-select: none;
+  position: relative;
+  z-index: 10;
+}
+
+.tab-list {
+  display: flex;
+  align-items: flex-end;
+  overflow-x: auto;
+  overflow-y: visible;  /* ← was: overflow-y: hidden */
+  flex: 1;
+  height: 100%;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.tab-list::-webkit-scrollbar {
+  display: none;
+}
+
+.tab-item {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  height: 32px;
+  padding: 0 8px 0 10px;
+  min-width: 100px;
+  max-width: 180px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-bottom: 1px solid transparent;
+  border-radius: 6px 6px 0 0;
+  cursor: pointer;
+  font-size: 13px;
+  color: var(--text-color);
+  white-space: nowrap;
+  /* overflow: hidden; <-- REMOVE THIS */
+  position: relative;
+  transition: background-color 0.15s ease, color 0.15s ease;
+  flex-shrink: 0;
+  margin-right: 2px;
+  opacity: 0.7;
+}
+
+.tab-item:hover {
+  background-color: var(--button-hover);
+  opacity: 0.9;
+}
+
+.tab-item.active {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+  border-bottom: 1px solid var(--bg-color);
+  opacity: 1;
+  z-index: 2;
+}
+
+.tab-item.unsaved::after {
+  content: '';
+  display: inline-block;
+  width: 6px;
+  height: 6px;
+  background-color: var(--accent-color);
+  border-radius: 50%;
+  flex-shrink: 0;
+  margin-left: 2px;
+}
+
+.tab-title {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  flex: 1;
+  min-width: 0;
+}
+
+.tab-close-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 16px;
+  height: 16px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 11px;
+  opacity: 0;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+}
+
+.tab-item:hover .tab-close-btn,
+.tab-item.active .tab-close-btn {
+  opacity: 0.6;
+}
+
+.tab-close-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-new-btn {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  height: 24px;
+  padding: 0 8px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 12px;
+  flex-shrink: 0;
+  margin-left: 6px;
+  align-self: center;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tab-new-btn:hover {
+  background-color: rgba(46, 160, 67, 0.1);
+  border-color: var(--accent-color, #2ea043);
+  color: var(--accent-color, #2ea043);
+}
+
+.tab-new-btn:active {
+  background-color: rgba(46, 160, 67, 0.2);
+}
+
+/* Drag-and-drop visual feedback */
+.tab-item.dragging {
+  opacity: 0.4;
+}
+
+.tab-item.drag-over {
+  border-left: 2px solid var(--accent-color);
+}
+
+/* Tab enter animation */
+@keyframes tabSlideIn {
+  from { opacity: 0; transform: translateY(4px); }
+  to   { opacity: 0.7; transform: translateY(0); }
+}
+
+.tab-item {
+  animation: tabSlideIn 0.12s ease forwards;
+}
+
+.tab-item.active {
+  animation: none;
+}
+
+/* Hide tab bar on very small screens — single-file use */
+@media (max-width: 480px) {
+  .tab-bar {
+    display: none;
+  }
+}
+
+/* ========================================
+   TAB OVERFLOW — Scroll Buttons & Fade Indicators
+   ======================================== */
+
+.tab-scroll-btn {
+  display: none;
+  align-items: center;
+  justify-content: center;
+  width: 24px;
+  height: 24px;
+  border-radius: 4px;
+  background: none;
+  border: 1px solid transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 14px;
+  flex-shrink: 0;
+  padding: 0;
+  transition: background-color 0.15s ease, border-color 0.15s ease, opacity 0.15s ease;
+  z-index: 2;
+  opacity: 0.6;
+}
+
+.tab-scroll-btn:hover {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+  opacity: 1;
+}
+
+.tab-scroll-btn:active {
+  background-color: var(--button-active);
+}
+
+/* Show scroll buttons only when overflow exists */
+.tab-bar.has-overflow-left .tab-scroll-left,
+.tab-bar.has-overflow-right .tab-scroll-right {
+  display: flex;
+}
+
+/* Overflow fade indicators — subtle gradient at clipped edges */
+.tab-list::before,
+.tab-list::after {
+  content: '';
+  position: sticky;
+  top: 0;
+  bottom: 0;
+  width: 0;
+  flex-shrink: 0;
+  pointer-events: none;
+  z-index: 3;
+  transition: box-shadow 0.2s ease;
+}
+
+.tab-list::before {
+  left: 0;
+}
+
+.tab-list::after {
+  right: 0;
+}
+
+.tab-bar.has-overflow-left .tab-list::before {
+  box-shadow: 8px 0 12px -4px rgba(0, 0, 0, 0.12);
+}
+
+.tab-bar.has-overflow-right .tab-list::after {
+  box-shadow: -8px 0 12px -4px rgba(0, 0, 0, 0.12);
+}
+
+[data-theme="dark"] .tab-bar.has-overflow-left .tab-list::before {
+  box-shadow: 8px 0 12px -4px rgba(0, 0, 0, 0.35);
+}
+
+[data-theme="dark"] .tab-bar.has-overflow-right .tab-list::after {
+  box-shadow: -8px 0 12px -4px rgba(0, 0, 0, 0.35);
+}
+
+/* ========================================
+   THREE-DOT TAB MENU
+   ======================================== */
+
+.tab-menu-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 22px;
+  height: 22px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 14px;
+  font-weight: bold;
+  letter-spacing: 1px;
+  opacity: 0.65;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+  position: relative;
+}
+
+/* Touch Hitbox Expansion for Tab Menu Button */
+.tab-menu-btn::before {
+  content: '';
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  width: 48px;
+  height: 48px;
+}
+
+/* Touch-optimized styling for coarser pointers (e.g., smartphones & tablets) */
+@media (pointer: coarse) {
+  .tab-bar {
+    height: 40px !important;
+  }
+  .tab-item {
+    height: 40px !important;
+    font-size: 14px !important;
+    padding: 0 10px 0 12px !important;
+    gap: 8px !important;
+  }
+  .tab-new-btn,
+  .tab-reset-btn {
+    height: 32px !important;
+    font-size: 14px !important;
+    padding: 0 12px !important;
+  }
+  .tab-scroll-btn {
+    width: 32px !important;
+    height: 32px !important;
+    font-size: 18px !important;
+  }
+  .tab-menu-btn {
+    width: 30px !important;
+    height: 30px !important;
+    font-size: 18px !important;
+  }
+  .tab-close-btn {
+    width: 20px !important;
+    height: 20px !important;
+    font-size: 13px !important;
+    opacity: 0.8 !important;
+  }
+}
+
+.tab-item:hover .tab-menu-btn,
+.tab-item.active .tab-menu-btn {
+  opacity: 0.65;
+}
+
+.tab-menu-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+}
+
+.tab-menu-dropdown {
+  display: none;
+  position: fixed;
+  min-width: 130px;
+  background-color: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
+  z-index: 99999;
+  overflow: hidden;
+  flex-direction: column;
+}
+
+.tab-menu-dropdown.open {
+  display: flex;
+}
+
+.tab-menu-item {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  padding: 7px 12px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  text-align: left;
+  transition: background-color 0.12s ease;
+  white-space: nowrap;
+}
+
+.tab-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.tab-menu-item-danger {
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-menu-item-danger:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+}
+
+/* ========================================
+   RESET BUTTON
+   ======================================== */
+
+.tab-reset-btn {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  height: 24px;
+  padding: 0 8px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 12px;
+  flex-shrink: 0;
+  margin-left: 6px;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tab-reset-btn:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: var(--color-danger-fg, #d73a49);
+}
+
+/* ========================================
+   RESET & RENAME CONFIRMATION MODALS
+   ======================================== */
+
+.reset-modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.45);
+  z-index: 2000;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.reset-modal-overlay.modal-overlay {
+  opacity: 0;
+  visibility: hidden;
+  transition: opacity 0.2s ease, visibility 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible {
+  opacity: 1;
+  visibility: visible;
+}
+
+.reset-modal-box {
+  background: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 24px 28px;
+  min-width: 280px;
+  max-width: 360px;
+  box-shadow: 0 8px 32px rgba(0,0,0,0.25);
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+}
+
+.modal-box {
+  max-height: min(85vh, 760px);
+  opacity: 0;
+  transform: translateY(8px);
+  transition: transform 0.2s ease, opacity 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible .modal-box {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+.modal-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.modal-header .reset-modal-message {
+  text-align: left;
+  flex: 1;
+}
+
+.modal-close-btn {
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  border-radius: 6px;
+  width: 28px;
+  height: 28px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.modal-close-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.modal-body {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(60vh, 520px);
+  overflow: auto;
+  padding-right: 4px;
+}
+
+.modal-section {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.modal-section-title {
+  margin: 0;
+  font-size: 0.95rem;
+  font-weight: 600;
+}
+
+.modal-list {
+  margin: 0;
+  padding-left: 1.1rem;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  font-size: 0.85rem;
+}
+
+.modal-list a {
+  color: var(--accent-color);
+  text-decoration: none;
+}
+
+.modal-list a:hover {
+  text-decoration: underline;
+}
+
+.modal-subtext {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  line-height: 1.4;
+}
+
+.find-replace-meta {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.find-replace-nav {
+  display: inline-flex;
+  gap: 6px;
+}
+
+.find-nav-btn {
+  width: 28px;
+  height: 28px;
+  padding: 0;
+}
+
+.about-header {
+  display: flex;
+  align-items: center;
+  gap: 16px;
+  flex-wrap: wrap;
+}
+
+.about-logo {
+  width: 64px;
+  height: 64px;
+  border-radius: 12px;
+  border: 1px solid var(--border-color);
+  object-fit: cover;
+}
+
+.about-details {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.about-title {
+  margin: 0;
+  font-size: 1.05rem;
+  font-weight: 600;
+}
+
+.about-description {
+  margin: 0;
+  font-size: 0.85rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.about-meta {
+  margin: 0;
+  font-size: 0.78rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.modal-body kbd {
+  padding: 2px 6px;
+  border-radius: 4px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  font-size: 0.75rem;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+}
+
+.reset-modal-box--wide {
+  width: min(92vw, 640px);
+  max-width: 640px;
+}
+
+.reset-modal-message {
+  margin: 0;
+  font-size: 14px;
+  color: var(--text-color);
+  font-weight: 500;
+  text-align: center;
+}
+
+.reset-modal-actions {
+  display: flex;
+  gap: 10px;
+  justify-content: flex-end;
+}
+
+.reset-modal-btn {
+  padding: 6px 16px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  font-size: 13px;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.reset-modal-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.reset-modal-confirm {
+  background-color: var(--color-danger-fg, #d73a49);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: #fff;
+}
+
+.reset-modal-confirm:hover {
+  background-color: #b02a37;
+  border-color: #b02a37;
+}
+
+/* ========================================
+   PDF EXPORT PROGRESS MODAL
+   ======================================== */
+
+.pdf-progress-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 2600;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(0, 0, 0, 0.45);
+  padding: 20px;
+}
+
+.pdf-progress-modal {
+  width: min(92vw, 420px);
+  background: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.28);
+  color: var(--text-color);
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  padding: 20px;
+}
+
+.pdf-progress-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.pdf-progress-title {
+  margin: 0;
+  font-size: 15px;
+  font-weight: 600;
+}
+
+.pdf-progress-percent {
+  font-size: 28px;
+  font-weight: 600;
+  line-height: 1;
+}
+
+.pdf-progress-track {
+  width: 100%;
+  height: 10px;
+  background: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 999px;
+  overflow: hidden;
+}
+
+.pdf-progress-fill {
+  width: 0%;
+  height: 100%;
+  background: var(--accent-color);
+  border-radius: inherit;
+  transition: width 0.18s ease;
+}
+
+.pdf-progress-details {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary);
+}
+
+.pdf-progress-detail {
+  display: flex;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.pdf-progress-detail strong {
+  color: var(--text-color);
+  font-weight: 600;
+}
+
+.pdf-progress-actions {
+  display: flex;
+  justify-content: flex-end;
+}
+
+.tool-button.pdf-export-loading,
+.mobile-menu-item.pdf-export-loading {
+  pointer-events: none;
+}
+/* ========================================
+   RESET MODAL FORM FIELDS
+   ======================================== */
+
+.reset-modal-field {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  text-align: left;
+}
+
+.reset-modal-field-group {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.reset-modal-label {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  font-weight: 600;
+}
+
+.reset-modal-toggle-group {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.reset-modal-option {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 13px;
+  color: var(--text-color);
+}
+
+.reset-modal-option input {
+  margin: 0;
+}
+
+/* ========================================
+   RENAME MODAL INPUT
+   ======================================== */
+
+.rename-modal-input {
+  width: 100%;
+  padding: 7px 10px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  color: var(--text-color);
+  font-size: 13px;
+  outline: none;
+  box-sizing: border-box;
+}
+
+.rename-modal-input:focus {
+  border-color: var(--accent-color);
+}
+
+/* ========================================
+   TOOLBAR POPUP PANELS
+   ======================================== */
+
+.reset-modal-box--xl {
+  width: min(94vw, 980px);
+  max-width: 980px;
+}
+
+.modal-empty {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
+  gap: 12px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px;
+}
+
+.symbol-grid {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px 2px;
+}
+
+.symbol-section-title {
+  margin: 0;
+  font-size: 11px;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--text-secondary, #57606a);
+}
+
+.symbol-section-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+  gap: 12px;
+}
+
+.alert-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
+  gap: 12px;
+  max-height: min(45vh, 360px);
+  overflow: auto;
+  padding: 2px;
+}
+
+.emoji-item,
+.symbol-item,
+.alert-option {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  align-items: center;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 10px;
+  background: var(--bg-color);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
+}
+
+.emoji-item:focus-visible,
+.symbol-item:focus-visible,
+.alert-option:focus-visible {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+.emoji-item.is-selected,
+.symbol-item.is-selected,
+.alert-option.is-selected {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
+  background-color: rgba(88, 166, 255, 0.08);
+}
+
+.emoji-preview {
+  width: 36px;
+  height: 36px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.emoji-preview img {
+  width: 32px;
+  height: 32px;
+}
+
+.emoji-shortcode {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-copy-btn,
+.symbol-copy-btn {
+  border: none;
+  background: transparent;
+  color: var(--text-secondary, #57606a);
+  cursor: pointer;
+  padding: 2px;
+  border-radius: 4px;
+}
+
+.emoji-copy-btn:hover,
+.symbol-copy-btn:hover {
+  color: var(--text-color);
+  background: var(--button-hover);
+}
+
+.emoji-copy-btn.is-copied,
+.symbol-copy-btn.is-copied {
+  color: var(--accent-color);
+}
+
+.symbol-preview {
+  font-size: 28px;
+  line-height: 1;
+}
+
+.symbol-code {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.alert-option {
+  align-items: stretch;
+  text-align: left;
+  padding: 12px;
+}
+
+.alert-preview {
+  margin: 0;
+}
+
+.alert-preview .markdown-alert {
+  padding: 0.5rem 0.9rem;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.alert-preview .markdown-alert-title {
+  margin: 0 0 6px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.alert-preview .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.alert-preview .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.alert-preview .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--text-color);
+}
+
+.alert-preview .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.alert-preview .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.alert-preview .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.alert-preview .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.alert-preview .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-note {
+  color: #4493f8;
+  border-left-color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-tip {
+  color: #3fb950;
+  border-left-color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-important {
+  color: #ab7df8;
+  border-left-color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-warning {
+  color: #d29922;
+  border-left-color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-caution {
+  color: #f85149;
+  border-left-color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+}
+
+.github-import-error {
+  margin: 0;
+  font-size: 12px;
+  color: var(--color-danger-fg, #d73a49);
+  text-align: left;
+  line-height: 1.5;
+}
+
+.github-import-error.is-info {
+  color: var(--text-secondary, #57606a);
+}
+
+#github-import-modal .reset-modal-box {
+  width: 60vw;
+  max-width: 60vw;
+  min-width: 340px;
+  padding: 30px 34px;
+  gap: 16px;
+  box-shadow: 0 20px 48px rgba(0, 0, 0, 0.22);
+}
+
+#github-import-modal .reset-modal-message {
+  font-size: 18px;
+  line-height: 1.35;
+  text-align: left;
+}
+
+#github-import-url,
+#github-import-file-select {
+  min-height: 46px;
+  padding: 10px 12px;
+  font-size: 15px;
+}
+
+#github-import-file-select {
+  min-height: 180px;
+}
+
+.github-import-tree {
+  max-height: 420px;
+  overflow: auto;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 12px;
+  background: var(--bg-color);
+}
+
+.github-import-selection-toolbar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  padding: 10px 12px;
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  background: var(--button-bg);
+}
+
+.github-import-selected-count {
+  font-size: 14px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.github-import-tree ul {
+  list-style: none;
+  margin: 0;
+  padding-left: 18px;
+}
+
+.github-import-tree > ul {
+  padding-left: 4px;
+}
+
+.github-import-tree li {
+  margin: 2px 0;
+}
+
+.github-tree-folder-label {
+  display: inline-block;
+  font-size: 14px;
+  color: var(--text-secondary, #57606a);
+  margin-bottom: 4px;
+}
+
+.github-tree-file-btn {
+  border: 0;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 6px 8px;
+  border-radius: 6px;
+  text-align: left;
+  width: 100%;
+  font-size: 14px;
+}
+
+.github-tree-file-btn:hover,
+.github-tree-file-btn:focus-visible {
+  background: var(--button-hover);
+  outline: none;
+}
+
+.github-tree-file-btn.is-selected {
+  background: rgba(56, 139, 253, 0.14);
+  color: var(--accent-color);
+}
+
+#github-import-modal .reset-modal-actions {
+  gap: 12px;
+}
+
+#github-import-modal .reset-modal-btn {
+  min-height: 42px;
+  padding: 9px 18px;
+  font-size: 14px;
+}
+
+@media (max-width: 576px) {
+  #github-import-modal .reset-modal-box {
+    width: 95vw;
+    max-width: 95vw;
+    min-width: 0;
+    padding: 20px;
+    gap: 14px;
+  }
+
+  .github-import-selection-toolbar {
+    flex-direction: column;
+    align-items: stretch;
+  }
+
+  #github-import-modal .reset-modal-message {
+    font-size: 16px;
+  }
+
+  #github-import-modal .reset-modal-actions {
+    flex-direction: column-reverse;
+  }
+
+  #github-import-modal .reset-modal-btn {
+    width: 100%;
+  }
+}
+
+.frontmatter-table {
+  border-collapse: collapse;
+  margin-bottom: 1.5em;
+  font-size: 0.9em;
+  width: auto;
+  max-width: 100%;
+}
+
+.frontmatter-table th,
+.frontmatter-table td {
+  border: 1px solid var(--border-color);
+  padding: 6px 13px;
+  vertical-align: top;
+  color: var(--text-color);
+}
+
+.frontmatter-table tr:nth-child(odd) th,
+.frontmatter-table tr:nth-child(odd) td {
+  background-color: var(--table-bg);
+}
+
+.frontmatter-table tr:nth-child(even) th,
+.frontmatter-table tr:nth-child(even) td {
+  background-color: var(--editor-bg);
+}
+
+.frontmatter-table th {
+  font-weight: 600;
+  text-align: right;
+  white-space: nowrap;
+  vertical-align: middle;
+}
+
+.frontmatter-table td {
+  text-align: left;
+}
+
+.fm-complex {
+  margin: 0;
+  padding: 4px 6px;
+  font-size: 0.8em;
+  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  white-space: pre-wrap;
+  word-break: break-word;
+  background: transparent;
+  border: none;
+  color: var(--text-color);
+}
+
+.fm-tag {
+  display: inline-block;
+  padding: 2px 8px;
+  margin: 2px 3px 2px 0;
+  border: 1px solid var(--border-color);
+  border-radius: 2em;
+  font-size: 0.8em;
+  font-weight: 500;
+  color: var(--accent-color);
+  background-color: var(--button-bg);
+  white-space: nowrap;
+}
+
+/* ========================================
+   RTL SUPPORT
+   ======================================== */
+
+[dir="rtl"] body {
+  direction: rtl;
+}
+
+[dir="rtl"] .editor-pane {
+  padding-left: 0px;
+  padding-right: 20px;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor,
+[dir="rtl"] .markdown-body {
+  direction: rtl;
+  text-align: right;
+}
+
+[dir="rtl"] .markdown-body pre,
+[dir="rtl"] .markdown-body code,
+[dir="rtl"] .fm-complex {
+  direction: ltr;
+  text-align: left;
+}
+
+[dir="rtl"] .line-numbers {
+  left: auto;
+  right: 20px;
+  padding: 10px 0 10px 8px;
+  text-align: left;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor {
+  padding-left: 10px;
+  padding-right: calc(10px + var(--line-number-gutter));
+}
+
+[dir="rtl"] .editor-highlight-layer {
+  inset: 20px calc(20px + var(--line-number-gutter)) 20px 0;
+}
+
+[dir="rtl"] .mobile-menu-item,
+[dir="rtl"] .tab-menu-item,
+[dir="rtl"] .modal-header .reset-modal-message,
+[dir="rtl"] .reset-modal-field,
+[dir="rtl"] .alert-option,
+[dir="rtl"] .github-import-error,
+[dir="rtl"] #github-import-modal .reset-modal-message,
+[dir="rtl"] .github-tree-file-btn,
+[dir="rtl"] .frontmatter-table td {
+  text-align: right;
+}
+
+[dir="rtl"] .github-import-tree ul {
+  padding-left: 0;
+  padding-right: 18px;
+}
+
+[dir="rtl"] .github-import-tree > ul {
+  padding-right: 4px;
+}
+
+[dir="rtl"] .markdown-body .markdown-alert,
+[dir="rtl"] .alert-preview .markdown-alert {
+  border-left: 0;
+  border-right: 0.25em solid currentColor;
+}
+
+/* ============================================
+   SHARE MODAL
+   ============================================ */
+
+.share-modal-description {
+  font-size: 13px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+}
+
+.share-mode-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.share-mode-card {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 12px 14px;
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  cursor: pointer;
+  transition: border-color 0.15s ease, background-color 0.15s ease;
+  user-select: none;
+}
+
+.share-mode-card:hover {
+  border-color: var(--accent-color);
+  background: var(--button-hover);
+}
+
+.share-mode-card.is-selected {
+  border-color: var(--accent-color);
+  background: color-mix(in srgb, var(--accent-color) 8%, transparent);
+}
+
+.share-mode-card input[type="radio"] {
+  display: none;
+}
+
+.share-card-icon {
+  font-size: 18px;
+  width: 28px;
+  text-align: center;
+  color: var(--text-secondary, #57606a);
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-icon {
+  color: var(--accent-color);
+}
+
+.share-card-body {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  flex: 1;
+  min-width: 0;
+}
+
+.share-card-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.share-card-desc {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.share-card-check {
+  width: 18px;
+  text-align: center;
+  color: var(--accent-color);
+  opacity: 0;
+  transition: opacity 0.15s ease;
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-check {
+  opacity: 1;
+}
+
+.share-url-row {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.share-url-input {
+  flex: 1;
+  font-size: 12px;
+  font-family: var(--font-mono, monospace);
+  color: var(--text-secondary, #57606a);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.share-copy-btn {
+  flex-shrink: 0;
+  padding: 6px 10px;
+}
+
+.share-copy-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.share-modal-notice {
+  font-size: 11px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+  display: flex;
+  align-items: center;
+  gap: 5px;
+}
+
+/* ==========================================================================
+   Multilingual & CJK Optimization styles added by Aegis SEO agency
+   ========================================================================== */
+.lang-select-item {
+  display: flex !important;
+  align-items: center;
+  gap: 8px;
+  cursor: pointer;
+  transition: background-color 0.2s ease, padding-left 0.2s ease;
+}
+
+.lang-select-item:hover {
+  padding-left: 12px;
+}
+
+.lang-select-item.active {
+  background-color: var(--accent-color) !important;
+  color: #ffffff !important;
+  font-weight: 600;
+}
+
+/* Adjust CJK text layout for maximum readability inside the preview pane */
+html[lang="zh"] .markdown-body,
+html[lang="ja"] .markdown-body,
+html[lang="ko"] .markdown-body {
+  line-height: 1.75 !important;
+  letter-spacing: 0.03em;
+  word-break: keep-all;
+  overflow-wrap: break-word;
+  text-align: justify;
+}
+
+/* Specific heading spacing improvements for CJK characters */
+html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
+html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
+html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
+  font-weight: 700;
+  letter-spacing: 0.02em;
+  margin-top: 1.4em;
+  margin-bottom: 0.6em;
+}
+
+/* Smooth fade and scale transition for dropdown active states */
+.dropdown-menu {
+  opacity: 0;
+  transform: translateY(8px) scale(0.98);
+  display: block;
+  visibility: hidden;
+  transition: opacity 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.2s;
+}
+
+.dropdown-menu.show {
+  opacity: 1;
+  transform: translateY(0) scale(1);
+  visibility: visible;
+}
+
 /* ========================================
-   PDF EXPORT PROGRESS MODAL
+   FIND & REPLACE FLOATING PANEL DESIGN
    ======================================== */
 
-.pdf-progress-overlay {
+.find-replace-panel {
   position: fixed;
-  inset: 0;
-  z-index: 2600;
+  top: 100px;
+  right: 20px;
+  width: 340px;
+  background-color: var(--fr-bg);
+  border: 1px solid var(--fr-border);
+  border-radius: 12px;
+  box-shadow: var(--fr-shadow);
+  z-index: 1050;
+  display: flex;
+  flex-direction: column;
+  backdrop-filter: blur(10px);
+  -webkit-backdrop-filter: blur(10px);
+  transition: opacity 0.2s ease, transform 0.2s ease;
+  user-select: none;
+  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+}
+
+.find-replace-panel.docked {
+  position: relative;
+  top: 0 !important;
+  right: 0 !important;
+  height: 100%;
+  border-radius: 0;
+  border-top: none;
+  border-bottom: none;
+  border-right: none;
+  border-left: 1px solid var(--fr-border);
+  box-shadow: none;
+  backdrop-filter: none;
+  z-index: 10;
+  flex-shrink: 0;
+}
+
+.find-replace-panel.docked #find-replace-reset,
+.find-replace-panel.docked #find-replace-reset-footer {
+  display: none !important;
+}
+
+.find-replace-header {
   display: flex;
   align-items: center;
-  justify-content: center;
-  background: rgba(0, 0, 0, 0.45);
-  padding: 20px;
+  justify-content: space-between;
+  padding: 8px 12px;
+  border-bottom: 1px solid var(--fr-border);
+  cursor: move;
+  background-color: var(--header-bg);
+  border-top-left-radius: 11px;
+  border-top-right-radius: 11px;
 }
 
-.pdf-progress-modal {
-  width: min(92vw, 420px);
-  background: var(--header-bg);
-  border: 1px solid var(--border-color);
-  border-radius: 8px;
-  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.28);
+.find-replace-panel.docked .find-replace-header {
+  cursor: default;
+  border-top-left-radius: 0;
+  border-top-right-radius: 0;
+}
+
+.find-replace-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.find-replace-header-actions {
+  display: flex;
+  gap: 4px;
+}
+
+.panel-icon-btn {
+  background: none;
+  border: none;
   color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: background-color 0.15s ease;
+}
+
+.panel-icon-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.find-replace-body {
+  padding: 12px;
   display: flex;
   flex-direction: column;
-  gap: 16px;
-  padding: 20px;
+  gap: 8px;
 }
 
-.pdf-progress-header {
+.find-replace-field-row {
+  display: flex;
+  flex-direction: column;
+  position: relative;
+}
+
+.find-input-container, .replace-input-container {
   display: flex;
   align-items: center;
-  justify-content: space-between;
-  gap: 12px;
+  border: 1px solid var(--fr-border);
+  border-radius: 6px;
+  background-color: var(--bg-color);
+  padding: 2px 4px;
+  width: 100%;
 }
 
-.pdf-progress-title {
-  margin: 0;
-  font-size: 15px;
+.find-input-container:focus-within, .replace-input-container:focus-within {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 3px rgba(9, 105, 218, 0.15);
+}
+
+.find-input-field {
+  flex: 1;
+  border: none;
+  background: transparent;
+  color: var(--text-color);
+  font-size: 13px;
+  padding: 4px 6px;
+  outline: none;
+  width: 50%;
+}
+
+.find-options-group {
+  display: flex;
+  gap: 2px;
+}
+
+.find-option-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 11px;
   font-weight: 600;
+  cursor: pointer;
+  padding: 2px 5px;
+  border-radius: 4px;
+  transition: background-color 0.12s ease, color 0.12s ease;
+  min-width: 22px;
+  height: 22px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
 }
 
-.pdf-progress-percent {
-  font-size: 28px;
+.find-option-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+.find-option-btn.active {
+  background-color: var(--fr-btn-active-bg);
+  color: var(--fr-btn-active);
+}
+
+.find-error-drawer {
+  background-color: var(--fr-error-bg);
+  border: 1px solid var(--fr-error-border);
+  border-radius: 6px;
+  padding: 6px 10px;
+  font-size: 11px;
+  color: var(--fr-text-danger);
+  line-height: 1.3;
+}
+
+.find-replace-meta-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 2px 4px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary);
+}
+
+.find-nav-group {
+  display: flex;
+  gap: 4px;
+}
+
+.find-nav-arrow-btn {
+  background: none;
+  border: 1px solid var(--fr-border);
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 8px;
+  border-radius: 4px;
+  transition: background-color 0.15s ease;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.find-nav-arrow-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.find-nav-arrow-btn:disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+}
+
+.find-drawer-toggle-row {
+  border-top: 1px solid var(--fr-border);
+  margin-top: 4px;
+  padding-top: 6px;
+}
+
+.drawer-toggle-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 12px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  padding: 2px 4px;
+  border-radius: 4px;
+  transition: color 0.15s ease;
+}
+
+.drawer-toggle-btn:hover {
+  color: var(--text-color);
+}
+
+.find-replace-drawer-content {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 4px 6px;
+  border-top: 1px dashed var(--fr-border);
+  margin-top: 2px;
+  padding-top: 8px;
+}
+
+.drawer-field {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.drawer-field.check-field {
+  flex-direction: row;
+  align-items: center;
+  gap: 6px;
+  padding: 2px 0;
+}
+
+.drawer-label {
+  font-size: 11px;
   font-weight: 600;
-  line-height: 1;
+  color: var(--text-secondary);
 }
 
-.pdf-progress-track {
+.drawer-select {
   width: 100%;
-  height: 10px;
-  background: var(--button-bg);
-  border: 1px solid var(--border-color);
-  border-radius: 999px;
-  overflow: hidden;
+  padding: 4px 6px;
+  border-radius: 4px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  font-size: 12px;
+  outline: none;
 }
 
-.pdf-progress-fill {
-  width: 0%;
-  height: 100%;
-  background: var(--accent-color);
-  border-radius: inherit;
-  transition: width 0.18s ease;
+.drawer-checkbox {
+  margin: 0;
+  cursor: pointer;
 }
 
-.pdf-progress-details {
+.drawer-label-checkbox {
+  font-size: 12px;
+  color: var(--text-color);
+  cursor: pointer;
+}
+
+.find-replace-actions-footer {
   display: flex;
-  flex-direction: column;
   gap: 6px;
+  padding: 8px 12px 12px 12px;
+  border-top: 1px solid var(--fr-border);
+  background-color: var(--header-bg);
+  border-bottom-left-radius: 11px;
+  border-bottom-right-radius: 11px;
+}
+
+.find-replace-panel.docked .find-replace-actions-footer {
+  border-bottom-left-radius: 0;
+  border-bottom-right-radius: 0;
+}
+
+.fr-action-btn {
+  flex: 1;
+  padding: 6px 8px;
   font-size: 12px;
-  color: var(--text-secondary);
+  font-weight: 500;
+  border-radius: 6px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--button-bg);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease, border-color 0.15s ease;
+  text-align: center;
 }
 
-.pdf-progress-detail {
+.fr-action-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.fr-action-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.fr-action-btn.secondary {
+  max-width: 60px;
+}
+
+/* ========================================
+   DIFF PREVIEW CONTAINER
+   ======================================== */
+.diff-preview-body {
+  padding: 16px;
   display: flex;
-  justify-content: space-between;
+  flex-direction: column;
   gap: 12px;
 }
 
-.pdf-progress-detail strong {
-  color: var(--text-color);
-  font-weight: 600;
+.diff-container {
+  border: 1px solid var(--fr-border);
+  border-radius: 8px;
+  background-color: var(--bg-color);
+  max-height: 400px;
+  overflow: auto;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 12px;
+  line-height: 1.5;
 }
 
-.pdf-progress-actions {
+.diff-line {
   display: flex;
-  justify-content: flex-end;
+  padding: 1px 8px;
 }
 
-.tool-button.pdf-export-loading,
-.mobile-menu-item.pdf-export-loading {
+.diff-line.addition {
+  background-color: rgba(46, 160, 67, 0.15);
+  color: #3fb950;
+}
+
+.diff-line.deletion {
+  background-color: rgba(248, 81, 73, 0.15);
+  color: #f85149;
+}
+
+.diff-line.context {
+  color: var(--text-secondary);
+}
+
+.diff-line-num {
+  width: 40px;
+  flex-shrink: 0;
+  text-align: right;
+  padding-right: 12px;
+  border-right: 1px solid var(--fr-border);
+  user-select: none;
+  opacity: 0.5;
+}
+
+.diff-line-content {
+  padding-left: 12px;
+  white-space: pre-wrap;
+  word-break: break-all;
+}
+
+/* ========================================
+   DOCK LAYOUT CODES
+   ======================================== */
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+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-dock-wrapper {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-pane-inner {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  position: relative;
+  overflow: hidden;
+}
+
+/* ========================================
+   MOBILE & TABLET FIND PANEL RESPONSIVE FIXES
+   ======================================== */
+@media (max-width: 1079px) {
+  #find-replace-dock {
+    display: none !important;
+  }
+}
+
+@media (max-width: 768px) {
+  /* Prevent full screen expansion of floating panel on small mobile viewports */
+  .find-replace-panel {
+    width: calc(100% - 24px) !important;
+    right: 12px !important;
+    left: 12px !important;
+    top: 80px !important;
+  }
+}
+
+/* ========================================
+   SKELETON LOADING SHIMMER SYSTEM
+   ======================================== */
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+  display: block;
+  background-color: var(--skeleton-bg);
+  border-radius: 6px;
+  position: relative;
+  overflow: hidden;
+  /* PERF-017: Removed skeleton-pulse; shimmer-only is sufficient and halves GPU compositing layers */
+  /* animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate; */
+}
+
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+  content: "";
+  position: absolute;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  left: 0;
+  transform: translateX(-100%);
+  background-image: linear-gradient(
+    90deg,
+    rgba(255, 255, 255, 0) 0%,
+    var(--skeleton-glow) 50%,
+    rgba(255, 255, 255, 0) 100%
+  );
+  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
+}
+
+@keyframes skeleton-shimmer {
+  100% {
+    transform: translateX(100%);
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+}
+
+@keyframes skeleton-pulse {
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+  }
+  50% {
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+  }
+}
+
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+  width: 32px;
+  height: 32px;
+  border-radius: 50%;
+  margin: 0 auto;
+}
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+.skeleton-text {
+  height: 12px;
+  width: 80%;
+  margin: 4px auto;
+  border-radius: 3px;
+}
+
+.skeleton-tree-folder {
+  height: 16px;
+  width: 140px;
+  margin: 6px 0;
+  display: inline-block;
+}
+
+.skeleton-tree-file {
+  height: 14px;
+  width: 180px;
+  margin: 4px 0 4px 12px;
+  display: inline-block;
+}
+
+/* Screen reader accessibility utility */
+.visually-hidden {
+  position: absolute !important;
+  width: 1px !important;
+  height: 1px !important;
+  padding: 0 !important;
+  margin: -1px !important;
+  overflow: hidden !important;
+  clip: rect(0, 0, 0, 0) !important;
+  clip-path: inset(50%) !important;
+  white-space: nowrap !important;
+  border: 0 !important;
+}
+
+/* Article skeleton layout structures */
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+  height: 28px;
+  width: 35%;
+  margin-bottom: 24px;
+  border-radius: 8px;
+}
+
+.skeleton-subtitle {
+  height: 20px;
+  width: 20%;
+  margin-bottom: 18px;
+  margin-top: 32px;
+  border-radius: 6px;
+}
+
+.skeleton-line {
+  height: 14px;
+  margin-bottom: 12px;
+  border-radius: 6px;
+}
+
+/* Symmetrical dynamic widths */
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+.skeleton-w92 { width: 92%; }
+.skeleton-w88 { width: 88%; }
+.skeleton-w85 { width: 85%; }
+.skeleton-w60 { width: 60%; }
+.skeleton-w45 { width: 45%; }
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+/* Editor pane skeleton overlay */
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+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  padding: 30px 24px 24px calc(24px + var(--line-number-gutter));
+  z-index: 10;
   pointer-events: none;
+  background: var(--editor-bg);
+  box-sizing: border-box;
+  overflow: hidden;
+  transition: opacity 0.3s ease;
+}
+
+.editor-pane:not(.is-loading) .editor-skeleton {
+  display: none;
+}
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+.editor-pane.is-loading textarea {
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+}
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+/* Preview pane skeleton container */
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+  display: block;
+  width: 100%;
+  box-sizing: border-box;
+  padding: 10px 4px;
+  background: transparent;
+  transition: opacity 0.3s ease;
+}
+
+/* Mermaid compilation loading states */
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+  min-height: 180px;
+  background-color: var(--skeleton-bg);
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  position: relative;
+  overflow: hidden;
+  animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate;
+}
+
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 }
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-[data-theme="dark"] .alert-preview .markdown-alert-note {
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-.share-card-check {
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-.share-url-input {
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-.share-copy-btn {
-  flex-shrink: 0;
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-.share-copy-btn:disabled {
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-.share-modal-notice {
-  font-size: 11px;
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-  margin: 0;
-  display: flex;
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-}
-
-/* ==========================================================================
-   Multilingual & CJK Optimization styles added by Aegis SEO agency
-   ========================================================================== */
-.lang-select-item {
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-.lang-select-item:hover {
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-.lang-select-item.active {
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-
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-html[lang="ja"] .markdown-body,
-html[lang="ko"] .markdown-body {
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-  word-break: keep-all;
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-
-/* Specific heading spacing improvements for CJK characters */
-html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
-html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
-html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
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-.dropdown-menu {
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-.dropdown-menu.show {
-  opacity: 1;
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-
-/* ========================================
-   FIND & REPLACE FLOATING PANEL DESIGN
-   ======================================== */
-
-.find-replace-panel {
-  position: fixed;
-  top: 100px;
-  right: 20px;
-  width: 340px;
-  background-color: var(--fr-bg);
-  border: 1px solid var(--fr-border);
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-  z-index: 1050;
-  display: flex;
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-  backdrop-filter: blur(10px);
-  -webkit-backdrop-filter: blur(10px);
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-  user-select: none;
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-
-.find-replace-panel.docked {
-  position: relative;
-  top: 0 !important;
-  right: 0 !important;
-  height: 100%;
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-  border-top: none;
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-
-.find-replace-panel.docked #find-replace-reset,
-.find-replace-panel.docked #find-replace-reset-footer {
-  display: none !important;
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-
-.find-replace-header {
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-  justify-content: space-between;
-  padding: 8px 12px;
-  border-bottom: 1px solid var(--fr-border);
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-.find-replace-panel.docked .find-replace-header {
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-
-.find-replace-title {
-  font-size: 13px;
-  font-weight: 600;
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-
-.find-replace-header-actions {
-  display: flex;
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-}
-
-.panel-icon-btn {
-  background: none;
-  border: none;
-  color: var(--text-color);
-  font-size: 12px;
-  cursor: pointer;
-  padding: 2px 6px;
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-
-.panel-icon-btn:hover {
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-}
-
-.find-replace-body {
-  padding: 12px;
-  display: flex;
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-
-.find-replace-field-row {
-  display: flex;
-  flex-direction: column;
-  position: relative;
-}
-
-.find-input-container, .replace-input-container {
-  display: flex;
-  align-items: center;
-  border: 1px solid var(--fr-border);
-  border-radius: 6px;
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-
-.find-input-container:focus-within, .replace-input-container:focus-within {
-  border-color: var(--accent-color);
-  box-shadow: 0 0 0 3px rgba(9, 105, 218, 0.15);
-}
-
-.find-input-field {
-  flex: 1;
-  border: none;
-  background: transparent;
-  color: var(--text-color);
-  font-size: 13px;
-  padding: 4px 6px;
-  outline: none;
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-}
-
-.find-options-group {
-  display: flex;
-  gap: 2px;
-}
-
-.find-option-btn {
-  background: none;
-  border: none;
-  color: var(--text-secondary);
-  font-size: 11px;
-  font-weight: 600;
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-  transition: background-color 0.12s ease, color 0.12s ease;
-  min-width: 22px;
-  height: 22px;
-  display: inline-flex;
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-}
-
-.find-option-btn:hover {
-  background-color: var(--button-hover);
-  color: var(--text-color);
-}
-
-.find-option-btn.active {
-  background-color: var(--fr-btn-active-bg);
-  color: var(--fr-btn-active);
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-
-.find-error-drawer {
-  background-color: var(--fr-error-bg);
-  border: 1px solid var(--fr-error-border);
-  border-radius: 6px;
-  padding: 6px 10px;
-  font-size: 11px;
-  color: var(--fr-text-danger);
-  line-height: 1.3;
-}
-
-.find-replace-meta-row {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  padding: 2px 4px;
-}
-
-.find-match-count {
-  font-size: 12px;
-  color: var(--text-secondary);
-}
-
-.find-nav-group {
-  display: flex;
-  gap: 4px;
-}
-
-.find-nav-arrow-btn {
-  background: none;
-  border: 1px solid var(--fr-border);
-  color: var(--text-color);
-  font-size: 12px;
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-  border-radius: 4px;
-  transition: background-color 0.15s ease;
-  display: flex;
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-  justify-content: center;
-}
-
-.find-nav-arrow-btn:hover:not(:disabled) {
-  background-color: var(--button-hover);
-}
-
-.find-nav-arrow-btn:disabled {
-  opacity: 0.4;
-  cursor: not-allowed;
-}
-
-.find-drawer-toggle-row {
-  border-top: 1px solid var(--fr-border);
-  margin-top: 4px;
-  padding-top: 6px;
-}
-
-.drawer-toggle-btn {
-  background: none;
-  border: none;
-  color: var(--text-secondary);
-  font-size: 12px;
-  cursor: pointer;
-  display: flex;
-  align-items: center;
-  padding: 2px 4px;
-  border-radius: 4px;
-  transition: color 0.15s ease;
-}
-
-.drawer-toggle-btn:hover {
-  color: var(--text-color);
-}
-
-.find-replace-drawer-content {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-  padding: 4px 6px;
-  border-top: 1px dashed var(--fr-border);
-  margin-top: 2px;
-  padding-top: 8px;
-}
-
-.drawer-field {
-  display: flex;
-  flex-direction: column;
-  gap: 4px;
-}
-
-.drawer-field.check-field {
-  flex-direction: row;
-  align-items: center;
-  gap: 6px;
-  padding: 2px 0;
-}
-
-.drawer-label {
-  font-size: 11px;
-  font-weight: 600;
-  color: var(--text-secondary);
-}
-
-.drawer-select {
-  width: 100%;
-  padding: 4px 6px;
-  border-radius: 4px;
-  border: 1px solid var(--fr-border);
-  background-color: var(--bg-color);
-  color: var(--text-color);
-  font-size: 12px;
-  outline: none;
-}
-
-.drawer-checkbox {
-  margin: 0;
-  cursor: pointer;
-}
-
-.drawer-label-checkbox {
-  font-size: 12px;
-  color: var(--text-color);
-  cursor: pointer;
-}
-
-.find-replace-actions-footer {
-  display: flex;
-  gap: 6px;
-  padding: 8px 12px 12px 12px;
-  border-top: 1px solid var(--fr-border);
-  background-color: var(--header-bg);
-  border-bottom-left-radius: 11px;
-  border-bottom-right-radius: 11px;
-}
-
-.find-replace-panel.docked .find-replace-actions-footer {
-  border-bottom-left-radius: 0;
-  border-bottom-right-radius: 0;
-}
-
-.fr-action-btn {
-  flex: 1;
-  padding: 6px 8px;
-  font-size: 12px;
-  font-weight: 500;
-  border-radius: 6px;
-  border: 1px solid var(--fr-border);
-  background-color: var(--button-bg);
-  color: var(--text-color);
-  cursor: pointer;
-  transition: background-color 0.15s ease, border-color 0.15s ease;
-  text-align: center;
-}
-
-.fr-action-btn:hover:not(:disabled) {
-  background-color: var(--button-hover);
-}
-
-.fr-action-btn:disabled {
-  opacity: 0.5;
-  cursor: not-allowed;
-}
-
-.fr-action-btn.secondary {
-  max-width: 60px;
-}
-
-/* ========================================
-   DIFF PREVIEW CONTAINER
-   ======================================== */
-.diff-preview-body {
-  padding: 16px;
-  display: flex;
-  flex-direction: column;
-  gap: 12px;
-}
-
-.diff-container {
-  border: 1px solid var(--fr-border);
-  border-radius: 8px;
-  background-color: var(--bg-color);
-  max-height: 400px;
-  overflow: auto;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 12px;
-  line-height: 1.5;
-}
-
-.diff-line {
-  display: flex;
-  padding: 1px 8px;
-}
-
-.diff-line.addition {
-  background-color: rgba(46, 160, 67, 0.15);
-  color: #3fb950;
-}
-
-.diff-line.deletion {
-  background-color: rgba(248, 81, 73, 0.15);
-  color: #f85149;
-}
-
-.diff-line.context {
-  color: var(--text-secondary);
-}
-
-.diff-line-num {
-  width: 40px;
-  flex-shrink: 0;
-  text-align: right;
-  padding-right: 12px;
-  border-right: 1px solid var(--fr-border);
-  user-select: none;
-  opacity: 0.5;
-}
-
-.diff-line-content {
-  padding-left: 12px;
-  white-space: pre-wrap;
-  word-break: break-all;
-}
-
-/* ========================================
-   DOCK LAYOUT CODES
-   ======================================== */
-.content-container {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-  position: relative;
-}
-
-.editor-dock-wrapper {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-  position: relative;
-}
-
-.editor-pane-inner {
-  display: flex;
-  flex-direction: column;
-  flex: 1;
-  position: relative;
-  overflow: hidden;
-}
-
-/* ========================================
-   MOBILE & TABLET FIND PANEL RESPONSIVE FIXES
-   ======================================== */
-@media (max-width: 1079px) {
-  #find-replace-dock {
-    display: none !important;
-  }
-}
-
-@media (max-width: 768px) {
-  /* Prevent full screen expansion of floating panel on small mobile viewports */
-  .find-replace-panel {
-    width: calc(100% - 24px) !important;
-    right: 12px !important;
-    left: 12px !important;
-    top: 80px !important;
-  }
-}
-
-/* ========================================
-   SKELETON LOADING SHIMMER SYSTEM
-   ======================================== */
-.skeleton-placeholder {
-  display: block;
-  background-color: var(--skeleton-bg);
-  border-radius: 6px;
-  position: relative;
-  overflow: hidden;
-  /* PERF-017: Removed skeleton-pulse; shimmer-only is sufficient and halves GPU compositing layers */
-  /* animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate; */
-}
-
-.skeleton-placeholder::after {
-  content: "";
-  position: absolute;
-  top: 0;
-  right: 0;
-  bottom: 0;
-  left: 0;
-  transform: translateX(-100%);
-  background-image: linear-gradient(
-    90deg,
-    rgba(255, 255, 255, 0) 0%,
-    var(--skeleton-glow) 50%,
-    rgba(255, 255, 255, 0) 100%
-  );
-  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
-}
-
-@keyframes skeleton-shimmer {
-  100% {
-    transform: translateX(100%);
-  }
-}
-
-@keyframes skeleton-pulse {
-  0%, 100% {
-    opacity: 1;
-  }
-  50% {
-    opacity: 0.82;
-  }
-}
-
-.skeleton-circle {
-  width: 32px;
-  height: 32px;
-  border-radius: 50%;
-  margin: 0 auto;
-}
-
-.skeleton-text {
-  height: 12px;
-  width: 80%;
-  margin: 4px auto;
-  border-radius: 3px;
-}
-
-.skeleton-tree-folder {
-  height: 16px;
-  width: 140px;
-  margin: 6px 0;
-  display: inline-block;
-}
-
-.skeleton-tree-file {
-  height: 14px;
-  width: 180px;
-  margin: 4px 0 4px 12px;
-  display: inline-block;
-}
-
-/* Screen reader accessibility utility */
-.visually-hidden {
-  position: absolute !important;
-  width: 1px !important;
-  height: 1px !important;
-  padding: 0 !important;
-  margin: -1px !important;
-  overflow: hidden !important;
-  clip: rect(0, 0, 0, 0) !important;
-  clip-path: inset(50%) !important;
-  white-space: nowrap !important;
-  border: 0 !important;
-}
-
-/* Article skeleton layout structures */
-.skeleton-title {
-  height: 28px;
-  width: 35%;
-  margin-bottom: 24px;
-  border-radius: 8px;
-}
-
-.skeleton-subtitle {
-  height: 20px;
-  width: 20%;
-  margin-bottom: 18px;
-  margin-top: 32px;
-  border-radius: 6px;
-}
-
-.skeleton-line {
-  height: 14px;
-  margin-bottom: 12px;
-  border-radius: 6px;
-}
-
-/* Symmetrical dynamic widths */
-.skeleton-w90 { width: 90%; }
-.skeleton-w92 { width: 92%; }
-.skeleton-w88 { width: 88%; }
-.skeleton-w85 { width: 85%; }
-.skeleton-w60 { width: 60%; }
-.skeleton-w45 { width: 45%; }
-
-/* Editor pane skeleton overlay */
-.editor-skeleton {
-  position: absolute;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  padding: 30px 24px 24px calc(24px + var(--line-number-gutter));
-  z-index: 10;
-  pointer-events: none;
-  background: var(--editor-bg);
-  box-sizing: border-box;
-  overflow: hidden;
-  transition: opacity 0.3s ease;
-}
-
-.editor-pane:not(.is-loading) .editor-skeleton {
-  display: none;
-}
-
-.editor-pane.is-loading textarea {
-  opacity: 0; /* Completely hide editor content while initial bootstrap skeleton runs */
-}
-
-/* Preview pane skeleton container */
-.skeleton-preview-container {
-  display: block;
-  width: 100%;
-  box-sizing: border-box;
-  padding: 10px 4px;
-  background: transparent;
-  transition: opacity 0.3s ease;
-}
-
-/* Mermaid compilation loading states */
-.mermaid-container.is-loading {
-  min-height: 180px;
-  background-color: var(--skeleton-bg);
-  border-radius: 8px;
-  border: 1px solid var(--border-color);
-  position: relative;
-  overflow: hidden;
-  animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate;
-}
-
-.mermaid-container.is-loading .mermaid {
-  opacity: 0; /* Hide raw chart source code during compile */
-}
-
-.mermaid-container.is-loading::after {
-  content: "";
-  position: absolute;
-  inset: 0;
-  transform: translateX(-100%);
-  background-image: linear-gradient(
-    90deg,
-    rgba(255, 255, 255, 0) 0%,
-    var(--skeleton-glow) 50%,
-    rgba(255, 255, 255, 0) 100%
-  );
-  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
-}
-
-/* Accessibility: respect user's motion preferences */
-@media (prefers-reduced-motion: reduce) {
-  .skeleton-placeholder,
-  .skeleton-placeholder::after,
-  .mermaid-container.is-loading,
-  .mermaid-container.is-loading::after {
-    animation: none;
-  }
-  .drag-overlay-inner {
-    animation: none;
-  }
-  .tab-item-new {
-    animation: none;
-  }
-  body,
-  .app-header,
-  .editor-pane,
-  .preview-pane,
-  .tool-button,
-  .markdown-tool-btn {
-    transition: none;
-  }
-}
-
\ No newline at end of file
+
+.mermaid-container.is-loading::after {
+  content: "";
+  position: absolute;
+  inset: 0;
+  transform: translateX(-100%);
+  background-image: linear-gradient(
+    90deg,
+    rgba(255, 255, 255, 0) 0%,
+    var(--skeleton-glow) 50%,
+    rgba(255, 255, 255, 0) 100%
+  );
+  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
+}
+
+/* Accessibility: respect user's motion preferences */
+@media (prefers-reduced-motion: reduce) {
+  .skeleton-placeholder,
+  .skeleton-placeholder::after,
+  .mermaid-container.is-loading,
+  .mermaid-container.is-loading::after {
+    animation: none;
+  }
+  .drag-overlay-inner {
+    animation: none;
+  }
+  .tab-item-new {
+    animation: none;
+  }
+  body,
+  .app-header,
+  .editor-pane,
+  .preview-pane,
+  .tool-button,
+  .markdown-tool-btn {
+    transition: none;
+  }
+}
+
+/* ========================================
+   BROWSER PRINT STYLES
+   ======================================== */
+@media print {
+  body * {
+    visibility: hidden;
+  }
+  #markdown-preview, #markdown-preview * {
+    visibility: visible;
+  }
+  #markdown-preview {
+    position: absolute;
+    left: 0;
+    top: 0;
+    width: 100% !important;
+    height: auto !important;
+    margin: 0 !important;
+    padding: 0 !important;
+    overflow: visible !important;
+    box-shadow: none !important;
+    border: none !important;
+    background: transparent !important;
+  }
+  .preview-pane {
+    position: static !important;
+    width: 100% !important;
+    height: auto !important;
+    overflow: visible !important;
+    margin: 0 !important;
+    padding: 0 !important;
+    box-shadow: none !important;
+    border: none !important;
+    background: transparent !important;
+  }
+  .content-container {
+    display: block !important;
+    position: static !important;
+    width: 100% !important;
+    height: auto !important;
+    overflow: visible !important;
+  }
+  header, .tab-bar, .markdown-format-toolbar, .editor-pane, .resize-divider, #line-numbers, .pdf-progress-overlay {
+    display: none !important;
+  }
+}
\ No newline at end of file
diff --git a/script.js b/script.js
index 4ddda0b6..7cbfd9bd 100644
--- a/script.js
+++ b/script.js
@@ -7964,18 +7964,51 @@ document.addEventListener("DOMContentLoaded", function () {
     return Promise.all(promises);
   }
 
-  // ============================================
-  // End Oversized Graphics Scaling Functions
-  // ============================================
+  function showLargePdfExportDialog(onChoosePrint, onChooseCanvas) {
+    const dialogOverlay = document.createElement("div");
+    dialogOverlay.className = "reset-modal-overlay";
+    dialogOverlay.style.display = "flex";
+    dialogOverlay.setAttribute("role", "dialog");
+    dialogOverlay.setAttribute("aria-modal", "true");
+
+    dialogOverlay.innerHTML = `
+      <div class="reset-modal-box reset-modal-box--wide">
+        <p class="reset-modal-message" style="font-weight: 600; margin-bottom: 0.5rem; color: var(--text-color);">Large Document Detected</p>
+        <p style="font-size: 0.9rem; margin-bottom: 1.5rem; opacity: 0.85; line-height: 1.4; color: var(--text-color);">
+          This document is very large. Generating a canvas-based PDF can take a long time and might cause browser lagging. 
+          <br><br>
+          We recommend using the <strong>Browser Print Dialog</strong> (select 'Save as PDF' as the destination). It is instant, uses vector graphics for perfectly sharp text, and has zero document size limits.
+        </p>
+        <div class="reset-modal-actions" style="display: flex; gap: 10px; justify-content: flex-end; flex-wrap: wrap;">
+          <button class="reset-modal-btn reset-modal-cancel" id="large-pdf-cancel" style="border: 1px solid var(--border-color); background: none; color: var(--text-color);">Cancel</button>
+          <button class="reset-modal-btn" id="large-pdf-canvas" style="background-color: var(--button-bg); border: 1px solid var(--border-color); color: var(--text-color);">Use Canvas (Slow)</button>
+          <button class="reset-modal-btn" id="large-pdf-print" style="background-color: var(--accent-color); border: none; color: #ffffff; font-weight: 600;">Browser Print (Recommended)</button>
+        </div>
+      </div>
+    `;
 
-  exportPdf.addEventListener("click", async function (event) {
-    event.preventDefault();
-    logPdfExportDebug("PDF export button clicked!");
-    if (activePdfExport) {
-      logPdfExportDebug("PDF export already active, ignoring click");
-      return;
-    }
+    document.body.appendChild(dialogOverlay);
 
+    const cleanup = () => {
+      dialogOverlay.remove();
+    };
+
+    dialogOverlay.querySelector("#large-pdf-cancel").addEventListener("click", () => {
+      cleanup();
+    });
+
+    dialogOverlay.querySelector("#large-pdf-canvas").addEventListener("click", () => {
+      cleanup();
+      onChooseCanvas();
+    });
+
+    dialogOverlay.querySelector("#large-pdf-print").addEventListener("click", () => {
+      cleanup();
+      onChoosePrint();
+    });
+  }
+
+  async function startCanvasPdfExport() {
     const progressState = createPdfProgressState();
     activePdfExport = progressState;
     setPdfExportTriggersBusy(progressState, true);
@@ -8237,6 +8270,32 @@ document.addEventListener("DOMContentLoaded", function () {
     } finally {
       cleanupPdfExport(progressState);
     }
+  }
+
+  exportPdf.addEventListener("click", async function (event) {
+    event.preventDefault();
+    logPdfExportDebug("PDF export button clicked!");
+    if (activePdfExport) {
+      logPdfExportDebug("PDF export already active, ignoring click");
+      return;
+    }
+
+    const markdown = markdownEditor.value;
+    // Set a threshold of 30,000 characters for large documents
+    if (markdown.length > 30000) {
+      showLargePdfExportDialog(
+        () => {
+          // Choice: Browser Print
+          window.print();
+        },
+        () => {
+          // Choice: Canvas rendering
+          startCanvasPdfExport();
+        }
+      );
+    } else {
+      startCanvasPdfExport();
+    }
   });
 
   copyMarkdownButton.addEventListener("click", function () {
diff --git a/styles.css b/styles.css
index aafd5a8a..c0c8401f 100644
--- a/styles.css
+++ b/styles.css
@@ -1,3873 +1,3918 @@
-:root {
-  --bg-color: #ffffff;
-  --editor-bg: #f6f8fa;
-  --preview-bg: #ffffff; /* Preview background for light mode */
-  --text-color: #24292e;
-  --text-secondary: #57606a;
-  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
-  --color-danger-fg: #d73a49;
-  --preview-text-color: #24292e; /* Text color for preview in light mode */
-  --border-color: #e1e4e8;
-  --header-bg: #f6f8fa;
-  --button-bg: #f6f8fa;
-  --button-hover: #e1e4e8;
-  --button-active: #d1d5da;
-  --scrollbar-thumb: #c1c1c1;
-  --scrollbar-track: #f1f1f1;
-  --accent-color: #0366d6;
-  --table-bg: #ffffff; /* Table background for light mode */
-  --code-bg: #f6f8fa; /* Code block background for light mode */
-  --skeleton-bg: #e2e8f0;
-  --skeleton-glow: rgba(255, 255, 255, 0.65);
-
-  /* Find & Replace Panel custom properties (PERF-010 consolidated) */
-  --fr-bg: rgba(255, 255, 255, 0.95);
-  --fr-border: #d0d7de;
-  --fr-shadow: 0 8px 24px rgba(140, 149, 159, 0.2);
-  --fr-btn-active: #0969da;
-  --fr-btn-active-bg: #ddf4ff;
-  --fr-match-highlight: #ffdf5d;
-  --fr-match-active: #ff9b30;
-  --fr-match-text-color: #24292e;
-  --fr-match-active-text-color: #24292e;
-  --fr-error-bg: #ffebe9;
-  --fr-error-border: #ff8577;
-  --fr-text-danger: #cf222e;
-}
-
-[data-theme="dark"] {
-  --bg-color: #0d1117;
-  --editor-bg: #161b22;
-  --preview-bg: #0d1117; /* Preview background for dark mode */
-  --text-color: #c9d1d9;
-  --text-secondary: #8b949e;
-  --color-danger-fg: #f85149;
-  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
-  --border-color: #30363d;
-  --header-bg: #161b22;
-  --button-bg: #21262d;
-  --button-hover: #30363d;
-  --button-active: #3b434b;
-  --scrollbar-thumb: #484f58;
-  --scrollbar-track: #21262d;
-  --accent-color: #58a6ff;
-  --table-bg: #161b22; /* Table background for dark mode */
-  --code-bg: #161b22; /* Code block background for dark mode */
-  --skeleton-bg: #2d3139;
-  --skeleton-glow: rgba(255, 255, 255, 0.08);
-
-  /* Find & Replace Panel custom properties for dark mode */
-  --fr-bg: rgba(28, 33, 40, 0.98);
-  --fr-border: #444c56;
-  --fr-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
-  --fr-btn-active: #2f81f7;
-  --fr-btn-active-bg: rgba(56, 139, 253, 0.15);
-  --fr-match-highlight: rgba(187, 128, 9, 0.4);
-  --fr-match-active: #ad6200;
-  --fr-match-text-color: #c9d1d9;
-  --fr-match-active-text-color: #ffffff;
-  --fr-error-bg: rgba(248, 81, 73, 0.1);
-  --fr-error-border: rgba(248, 81, 73, 0.4);
-  --fr-text-danger: #ff7b72;
-}
-
-* {
-  box-sizing: border-box;
-  margin: 0;
-  padding: 0;
-}
-
-@media (min-width: 768px) {
-  html,
-  body {
-    height: 100%;
-    overflow: hidden;
-  }
-}
-
-body {
-  background-color: var(--bg-color);
-  color: var(--text-color);
-  /* PERF-021: Removed background-color transition to avoid full-viewport repaint on theme toggle */
-  transition: color 0.15s ease;
-  min-height: 100vh;
-  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
-}
-
-.app-header {
-  background-color: var(--header-bg);
-  border-bottom: 1px solid var(--border-color);
-  padding: 0.35rem 0.75rem;
-  transition: background-color 0.3s ease;
-  position: relative;
-  z-index: 100;
-  flex-shrink: 0;
-}
-
-.app-container {
-  height: 100vh;
-  display: flex;
-  flex-direction: column;
-  overflow: hidden;
-}
-
-.content-container {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-}
-
-.editor-pane, .preview-pane {
-  flex: 1;
-  padding: 20px;
-  overflow-y: auto;
-  position: relative;
-  /* PERF-025: Shortened transition and scoped to background-color only */
-  transition: background-color 0.15s ease;
-}
-
-.editor-pane {
-  background-color: var(--editor-bg);
-  border-right: 1px solid var(--border-color);
-  padding-right: 0px;
-  --line-number-gutter: 0px;
-}
-
-.preview-pane {
-  background-color: var(--preview-bg); /* Using the new variable for preview background */
-}
-
-/* Custom scrollbar */
-.editor-pane::-webkit-scrollbar,
-.preview-pane::-webkit-scrollbar,
-#markdown-editor::-webkit-scrollbar {
-  width: 8px;
-  height: 8px;
-}
-
-.editor-pane::-webkit-scrollbar-track,
-.preview-pane::-webkit-scrollbar-track,
-#markdown-editor::-webkit-scrollbar-track {
-  background: var(--scrollbar-track);
-}
-
-.editor-pane::-webkit-scrollbar-thumb,
-.preview-pane::-webkit-scrollbar-thumb,
-#markdown-editor::-webkit-scrollbar-thumb {
-  background: var(--scrollbar-thumb);
-  border-radius: 4px;
-}
-
-.editor-pane::-webkit-scrollbar-thumb:hover,
-.preview-pane::-webkit-scrollbar-thumb:hover,
-#markdown-editor::-webkit-scrollbar-thumb:hover {
-  background: var(--button-active);
-}
-
-#markdown-editor {
-  width: 100%;
-  height: 100%;
-  border: none;
-  background-color: transparent;
-  color: var(--text-color);
-  resize: none;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 14px;
-  line-height: 1.5;
-  padding: 10px;
-  padding-left: calc(10px + var(--line-number-gutter));
-  transition: background-color 0.3s ease, color 0.3s ease;
-  overflow-y: auto;
-  position: relative;
-  z-index: 3;
-}
-
-#markdown-editor:focus {
-  outline: none;
-}
-
-.preview-pane {
-  padding: 20px;
-}
-
-.markdown-body {
-  padding: 20px;
-  width: 100%;
-  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
-  color: var(--preview-text-color); /* Using specific text color for preview content */
-}
-
-.markdown-body a.reference-link {
-  font-size: 0.75em;
-  letter-spacing: -0.02em;
-  line-height: 1;
-  vertical-align: super;
-  position: relative;
-  top: 0.08em;
-}
-
-/* Style tables in light mode */
-.markdown-body table {
-  background-color: var(--table-bg);
-  border-color: var(--border-color);
-}
-
-.markdown-body table tr {
-  background-color: var(--table-bg);
-  border-top: 1px solid var(--border-color);
-}
-
-.markdown-body table tr:nth-child(2n) {
-  background-color: var(--bg-color);
-}
-
-/* Style code blocks in light mode */
-.markdown-body pre {
-  background-color: var(--code-bg);
-  border-radius: 6px;
-}
-
-.markdown-body code {
-  background-color: var(--code-bg);
-  border-radius: 3px;
-  padding: 0.2em 0.4em;
-}
-
-.markdown-body img.emoji-inline {
-  width: 1em;
-  height: 1em;
-  vertical-align: -0.1em;
-}
-
-.markdown-body ul,
-.markdown-body ol {
-  padding-left: 2em;
-  margin: 0.4em 0;
-}
-
-.markdown-body ul ul,
-.markdown-body ul ol,
-.markdown-body ol ul,
-.markdown-body ol ol {
-  margin-top: 0.2em;
-  margin-bottom: 0.2em;
-}
-
-.markdown-body ul.contains-task-list,
-.markdown-body li.task-list-item {
-  list-style: none;
-}
-
-.markdown-body ul.contains-task-list {
-  padding-left: 2em;
-}
-
-.markdown-body li.task-list-item input[type="checkbox"] {
-  margin: 0 0.5em 0.2em 0;
-  vertical-align: middle;
-  pointer-events: none;
-}
-
-.markdown-body li.task-list-item::marker {
-  content: "";
-}
-
-.markdown-body li:has(> input[type="checkbox"]) {
-  list-style: none;
-}
-
-.markdown-body li:has(> input[type="checkbox"])::marker {
-  content: "";
-}
-
-.markdown-body ul:has(> li > input[type="checkbox"]) {
-  list-style: none;
-  padding-left: 2em;
-}
-
-.markdown-body .footnotes {
-  margin-top: 1.5rem;
-  font-size: 0.9em;
-}
-
-.markdown-body .footnotes ol {
-  padding-left: 1.5em;
-}
-
-.markdown-body .footnotes ol > li::marker {
-  content: "[" counter(list-item) "] ";
-  font-weight: 600;
-}
-
-.markdown-body .footnotes li > p {
-  margin: 0.2em 0;
-}
-
-.markdown-body .footnote-ref a,
-.markdown-body .footnote-backref {
-  text-decoration: none;
-}
-
-.markdown-body .footnote-backref {
-  margin-left: 0.4em;
-}
-
-.markdown-body .markdown-alert {
-  padding: 0.5rem 1rem;
-  margin-bottom: 16px;
-  border-left: 0.25em solid;
-  border-radius: 0.375rem;
-}
-
-.markdown-body .markdown-alert > :last-child {
-  margin-bottom: 0;
-}
-
-.markdown-body .markdown-alert-title {
-  margin: 0 0 8px;
-  font-weight: 600;
-  line-height: 1.25;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-}
-
-.markdown-body .markdown-alert-icon {
-  display: inline-flex;
-  width: 16px;
-  height: 16px;
-}
-
-.markdown-body .markdown-alert-icon svg {
-  width: 16px;
-  height: 16px;
-  fill: currentColor;
-}
-
-.markdown-body .markdown-alert-note {
-  color: #0969da;
-  border-left-color: #0969da;
-  background-color: #ddf4ff;
-}
-
-.markdown-body .markdown-alert-tip {
-  color: #1a7f37;
-  border-left-color: #1a7f37;
-  background-color: #dafbe1;
-}
-
-.markdown-body .markdown-alert-important {
-  color: #8250df;
-  border-left-color: #8250df;
-  background-color: #fbefff;
-}
-
-.markdown-body .markdown-alert-warning {
-  color: #9a6700;
-  border-left-color: #9a6700;
-  background-color: #fff8c5;
-}
-
-.markdown-body .markdown-alert-caution {
-  color: #cf222e;
-  border-left-color: #cf222e;
-  background-color: #ffebe9;
-}
-
-.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
-  color: var(--preview-text-color);
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-note {
-  color: #4493f8;
-  background-color: rgba(31, 111, 235, 0.15);
-  border-left-color: #4493f8;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-tip {
-  color: #3fb950;
-  background-color: rgba(35, 134, 54, 0.15);
-  border-left-color: #3fb950;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-important {
-  color: #ab7df8;
-  background-color: rgba(137, 87, 229, 0.15);
-  border-left-color: #ab7df8;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-warning {
-  color: #d29922;
-  background-color: rgba(210, 153, 34, 0.18);
-  border-left-color: #d29922;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-caution {
-  color: #f85149;
-  background-color: rgba(248, 81, 73, 0.18);
-  border-left-color: #f85149;
-}
-
-.toolbar {
-  display: flex;
-  gap: 8px;
-  align-items: center;
-}
-
-.toolbar-group {
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-}
-
-.toolbar-divider {
-  width: 1px;
-  height: 20px;
-  background-color: var(--border-color);
-  opacity: 0.7;
-}
-
-.tool-button {
-  background-color: var(--button-bg);
-  border: 1px solid var(--border-color);
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-  border-radius: 5px;
-  padding: 4px 8px;
-  font-size: 13px;
-  cursor: pointer;
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  gap: 4px;
-  /* PERF-016: Specific transition properties instead of 'all' to avoid animating layout-triggering properties */
-  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
-}
-
-.tool-button:hover {
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-.tool-button:active {
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-.tool-button:disabled,
-.tool-button[aria-disabled="true"] {
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-}
-
-.tool-button i {
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-
-.tool-button.is-active,
-.tool-button.is-active:hover {
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-  background-color: rgba(3, 102, 214, 0.08);
-}
-
-.btn-text {
-  display: none;
-}
-
-.toolbar .tool-button {
-  height: 28px;
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-}
-
-.toolbar .tool-button.sync-active {
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-  color: var(--accent-color);
-}
-
-.file-input {
-  display: none;
-}
-
-/* Drag overlay: full-screen drop target shown when user drags a file over the window */
-.drag-overlay {
-  display: none;
-  position: fixed;
-  inset: 0;
-  z-index: 9999;
-  background-color: rgba(0, 0, 0, 0.45);
-  pointer-events: none;
-  align-items: center;
-  justify-content: center;
-}
-
-.drag-overlay.active {
-  display: flex;
-  pointer-events: auto;
-}
-
-.drag-overlay-inner {
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-  border-radius: 12px;
-  padding: 48px 64px;
-  text-align: center;
-  color: #ffffff;
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-  animation: overlayPulse 1.4s ease-in-out infinite;
-}
-
-.drag-overlay-icon {
-  display: block;
-  font-size: 3rem;
-  margin-bottom: 12px;
-  color: var(--accent-color);
-}
-
-.drag-overlay-text {
-  font-size: 1.4rem;
-  font-weight: 600;
-  margin-bottom: 4px;
-}
-
-.drag-overlay-sub {
-  font-size: 0.85rem;
-  opacity: 0.75;
-  margin-bottom: 0;
-}
-
-@keyframes overlayPulse {
-  0%, 100% { transform: scale(1); }
-  50% { transform: scale(1.015); }
-}
-
-/* Editor drop hint: subtle text at bottom of editor pane, shown only when empty */
-.drop-hint {
-  position: absolute;
-  bottom: 14px;
-  left: 0;
-  right: 0;
-  text-align: center;
-  font-size: 0.75rem;
-  color: var(--text-color);
-  opacity: 0.35;
-  pointer-events: none;
-  user-select: none;
-  z-index: 3;
-}
-
-.editor-pane:has(#markdown-editor:not(:placeholder-shown)) .drop-hint {
-  display: none;
-}
-
-.line-numbers {
-  position: absolute;
-  top: 20px;
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-  width: var(--line-number-gutter);
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-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 14px;
-  line-height: 1.5;
-  text-align: right;
-  color: var(--text-secondary);
-  background-color: var(--editor-bg);
-  border-right: 1px solid var(--border-color);
-  box-sizing: border-box;
-  overflow: hidden;
-  pointer-events: none;
-  user-select: none;
-  z-index: 2;
-  font-variant-numeric: tabular-nums;
-}
-
-.line-numbers .line-number {
-  display: block;
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-}
-
-.editor-highlight-layer {
-  position: absolute;
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-  padding: 10px;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 14px;
-  line-height: 1.5;
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-  word-wrap: break-word;
-  color: transparent;
-  pointer-events: none;
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-  background-color: var(--editor-bg);
-  border-radius: 4px;
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-}
-
-.editor-highlight-layer::-webkit-scrollbar {
-  width: 8px;
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-}
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-.editor-highlight-layer::-webkit-scrollbar-thumb {
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-}
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-.editor-highlight-layer::-webkit-scrollbar-track {
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-.find-highlight {
-  background-color: var(--fr-match-highlight, rgba(255, 223, 93, 0.4)) !important;
-  border-radius: 2px;
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-.find-highlight.active {
-  background-color: var(--fr-match-active, #ff9b30) !important;
-  color: transparent !important;
-  padding: 0 !important;
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-}
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-.preview-find-highlight {
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-  border-radius: 2px;
-  padding: 0 1px !important;
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-}
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-.preview-find-highlight.active {
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-  outline: 1px solid var(--accent-color, #0366d6) !important;
-  outline-offset: -1px;
-}
-
-/* Dropdown improvements */
-.dropdown-menu {
-  background-color: var(--bg-color);
-  border-color: var(--border-color);
-}
-
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-.about-header {
-  display: flex;
-  align-items: center;
-  gap: 16px;
-  flex-wrap: wrap;
-}
-
-.about-logo {
-  width: 64px;
-  height: 64px;
-  border-radius: 12px;
-  border: 1px solid var(--border-color);
-  object-fit: cover;
-}
-
-.about-details {
-  display: flex;
-  flex-direction: column;
-  gap: 6px;
-}
-
-.about-title {
-  margin: 0;
-  font-size: 1.05rem;
-  font-weight: 600;
-}
-
-.about-description {
-  margin: 0;
-  font-size: 0.85rem;
-  color: var(--text-secondary, #57606a);
-}
-
-.about-meta {
-  margin: 0;
-  font-size: 0.78rem;
-  color: var(--text-secondary, #57606a);
-}
-
-.modal-body kbd {
-  padding: 2px 6px;
-  border-radius: 4px;
-  background-color: var(--button-bg);
-  border: 1px solid var(--border-color);
-  font-size: 0.75rem;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-}
-
-.reset-modal-box--wide {
-  width: min(92vw, 640px);
-  max-width: 640px;
-}
-
-.reset-modal-message {
-  margin: 0;
-  font-size: 14px;
-  color: var(--text-color);
-  font-weight: 500;
-  text-align: center;
-}
-
-.reset-modal-actions {
-  display: flex;
-  gap: 10px;
-  justify-content: flex-end;
-}
-
-.reset-modal-btn {
-  padding: 6px 16px;
-  border-radius: 6px;
-  border: 1px solid var(--border-color);
-  background: var(--button-bg);
-  color: var(--text-color);
-  font-size: 13px;
-  cursor: pointer;
-  transition: background-color 0.15s ease;
-}
-
-.reset-modal-btn:hover {
-  background-color: var(--button-hover);
-}
-
-.reset-modal-confirm {
-  background-color: var(--color-danger-fg, #d73a49);
-  border-color: var(--color-danger-fg, #d73a49);
-  color: #fff;
-}
-
-.reset-modal-confirm:hover {
-  background-color: #b02a37;
-  border-color: #b02a37;
-}
-
+:root {
+  --bg-color: #ffffff;
+  --editor-bg: #f6f8fa;
+  --preview-bg: #ffffff; /* Preview background for light mode */
+  --text-color: #24292e;
+  --text-secondary: #57606a;
+  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
+  --color-danger-fg: #d73a49;
+  --preview-text-color: #24292e; /* Text color for preview in light mode */
+  --border-color: #e1e4e8;
+  --header-bg: #f6f8fa;
+  --button-bg: #f6f8fa;
+  --button-hover: #e1e4e8;
+  --button-active: #d1d5da;
+  --scrollbar-thumb: #c1c1c1;
+  --scrollbar-track: #f1f1f1;
+  --accent-color: #0366d6;
+  --table-bg: #ffffff; /* Table background for light mode */
+  --code-bg: #f6f8fa; /* Code block background for light mode */
+  --skeleton-bg: #e2e8f0;
+  --skeleton-glow: rgba(255, 255, 255, 0.65);
+
+  /* Find & Replace Panel custom properties (PERF-010 consolidated) */
+  --fr-bg: rgba(255, 255, 255, 0.95);
+  --fr-border: #d0d7de;
+  --fr-shadow: 0 8px 24px rgba(140, 149, 159, 0.2);
+  --fr-btn-active: #0969da;
+  --fr-btn-active-bg: #ddf4ff;
+  --fr-match-highlight: #ffdf5d;
+  --fr-match-active: #ff9b30;
+  --fr-match-text-color: #24292e;
+  --fr-match-active-text-color: #24292e;
+  --fr-error-bg: #ffebe9;
+  --fr-error-border: #ff8577;
+  --fr-text-danger: #cf222e;
+}
+
+[data-theme="dark"] {
+  --bg-color: #0d1117;
+  --editor-bg: #161b22;
+  --preview-bg: #0d1117; /* Preview background for dark mode */
+  --text-color: #c9d1d9;
+  --text-secondary: #8b949e;
+  --color-danger-fg: #f85149;
+  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
+  --border-color: #30363d;
+  --header-bg: #161b22;
+  --button-bg: #21262d;
+  --button-hover: #30363d;
+  --button-active: #3b434b;
+  --scrollbar-thumb: #484f58;
+  --scrollbar-track: #21262d;
+  --accent-color: #58a6ff;
+  --table-bg: #161b22; /* Table background for dark mode */
+  --code-bg: #161b22; /* Code block background for dark mode */
+  --skeleton-bg: #2d3139;
+  --skeleton-glow: rgba(255, 255, 255, 0.08);
+
+  /* Find & Replace Panel custom properties for dark mode */
+  --fr-bg: rgba(28, 33, 40, 0.98);
+  --fr-border: #444c56;
+  --fr-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
+  --fr-btn-active: #2f81f7;
+  --fr-btn-active-bg: rgba(56, 139, 253, 0.15);
+  --fr-match-highlight: rgba(187, 128, 9, 0.4);
+  --fr-match-active: #ad6200;
+  --fr-match-text-color: #c9d1d9;
+  --fr-match-active-text-color: #ffffff;
+  --fr-error-bg: rgba(248, 81, 73, 0.1);
+  --fr-error-border: rgba(248, 81, 73, 0.4);
+  --fr-text-danger: #ff7b72;
+}
+
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+@media (min-width: 768px) {
+  html,
+  body {
+    height: 100%;
+    overflow: hidden;
+  }
+}
+
+body {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  /* PERF-021: Removed background-color transition to avoid full-viewport repaint on theme toggle */
+  transition: color 0.15s ease;
+  min-height: 100vh;
+  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
+}
+
+.app-header {
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  padding: 0.35rem 0.75rem;
+  transition: background-color 0.3s ease;
+  position: relative;
+  z-index: 100;
+  flex-shrink: 0;
+}
+
+.app-container {
+  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+}
+
+.editor-pane, .preview-pane {
+  flex: 1;
+  padding: 20px;
+  overflow-y: auto;
+  position: relative;
+  /* PERF-025: Shortened transition and scoped to background-color only */
+  transition: background-color 0.15s ease;
+}
+
+.editor-pane {
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  padding-right: 0px;
+  --line-number-gutter: 0px;
+}
+
+.preview-pane {
+  background-color: var(--preview-bg); /* Using the new variable for preview background */
+}
+
+/* Custom scrollbar */
+.editor-pane::-webkit-scrollbar,
+.preview-pane::-webkit-scrollbar,
+#markdown-editor::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-pane::-webkit-scrollbar-track,
+.preview-pane::-webkit-scrollbar-track,
+#markdown-editor::-webkit-scrollbar-track {
+  background: var(--scrollbar-track);
+}
+
+.editor-pane::-webkit-scrollbar-thumb,
+.preview-pane::-webkit-scrollbar-thumb,
+#markdown-editor::-webkit-scrollbar-thumb {
+  background: var(--scrollbar-thumb);
+  border-radius: 4px;
+}
+
+.editor-pane::-webkit-scrollbar-thumb:hover,
+.preview-pane::-webkit-scrollbar-thumb:hover,
+#markdown-editor::-webkit-scrollbar-thumb:hover {
+  background: var(--button-active);
+}
+
+#markdown-editor {
+  width: 100%;
+  height: 100%;
+  border: none;
+  background-color: transparent;
+  color: var(--text-color);
+  resize: none;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  padding: 10px;
+  padding-left: calc(10px + var(--line-number-gutter));
+  transition: background-color 0.3s ease, color 0.3s ease;
+  overflow-y: auto;
+  position: relative;
+  z-index: 3;
+}
+
+#markdown-editor:focus {
+  outline: none;
+}
+
+.preview-pane {
+  padding: 20px;
+}
+
+.markdown-body {
+  padding: 20px;
+  width: 100%;
+  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
+  color: var(--preview-text-color); /* Using specific text color for preview content */
+}
+
+.markdown-body a.reference-link {
+  font-size: 0.75em;
+  letter-spacing: -0.02em;
+  line-height: 1;
+  vertical-align: super;
+  position: relative;
+  top: 0.08em;
+}
+
+/* Style tables in light mode */
+.markdown-body table {
+  background-color: var(--table-bg);
+  border-color: var(--border-color);
+}
+
+.markdown-body table tr {
+  background-color: var(--table-bg);
+  border-top: 1px solid var(--border-color);
+}
+
+.markdown-body table tr:nth-child(2n) {
+  background-color: var(--bg-color);
+}
+
+/* Style code blocks in light mode */
+.markdown-body pre {
+  background-color: var(--code-bg);
+  border-radius: 6px;
+}
+
+.markdown-body code {
+  background-color: var(--code-bg);
+  border-radius: 3px;
+  padding: 0.2em 0.4em;
+}
+
+.markdown-body img.emoji-inline {
+  width: 1em;
+  height: 1em;
+  vertical-align: -0.1em;
+}
+
+.markdown-body ul,
+.markdown-body ol {
+  padding-left: 2em;
+  margin: 0.4em 0;
+}
+
+.markdown-body ul ul,
+.markdown-body ul ol,
+.markdown-body ol ul,
+.markdown-body ol ol {
+  margin-top: 0.2em;
+  margin-bottom: 0.2em;
+}
+
+.markdown-body ul.contains-task-list,
+.markdown-body li.task-list-item {
+  list-style: none;
+}
+
+.markdown-body ul.contains-task-list {
+  padding-left: 2em;
+}
+
+.markdown-body li.task-list-item input[type="checkbox"] {
+  margin: 0 0.5em 0.2em 0;
+  vertical-align: middle;
+  pointer-events: none;
+}
+
+.markdown-body li.task-list-item::marker {
+  content: "";
+}
+
+.markdown-body li:has(> input[type="checkbox"]) {
+  list-style: none;
+}
+
+.markdown-body li:has(> input[type="checkbox"])::marker {
+  content: "";
+}
+
+.markdown-body ul:has(> li > input[type="checkbox"]) {
+  list-style: none;
+  padding-left: 2em;
+}
+
+.markdown-body .footnotes {
+  margin-top: 1.5rem;
+  font-size: 0.9em;
+}
+
+.markdown-body .footnotes ol {
+  padding-left: 1.5em;
+}
+
+.markdown-body .footnotes ol > li::marker {
+  content: "[" counter(list-item) "] ";
+  font-weight: 600;
+}
+
+.markdown-body .footnotes li > p {
+  margin: 0.2em 0;
+}
+
+.markdown-body .footnote-ref a,
+.markdown-body .footnote-backref {
+  text-decoration: none;
+}
+
+.markdown-body .footnote-backref {
+  margin-left: 0.4em;
+}
+
+.markdown-body .markdown-alert {
+  padding: 0.5rem 1rem;
+  margin-bottom: 16px;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.markdown-body .markdown-alert > :last-child {
+  margin-bottom: 0;
+}
+
+.markdown-body .markdown-alert-title {
+  margin: 0 0 8px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.markdown-body .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.markdown-body .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.markdown-body .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.markdown-body .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.markdown-body .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.markdown-body .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.markdown-body .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--preview-text-color);
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-note {
+  color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+  border-left-color: #4493f8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-tip {
+  color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+  border-left-color: #3fb950;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-important {
+  color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+  border-left-color: #ab7df8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-warning {
+  color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+  border-left-color: #d29922;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-caution {
+  color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+  border-left-color: #f85149;
+}
+
+.toolbar {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.toolbar-group {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+}
+
+.toolbar-divider {
+  width: 1px;
+  height: 20px;
+  background-color: var(--border-color);
+  opacity: 0.7;
+}
+
+.tool-button {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 5px;
+  padding: 4px 8px;
+  font-size: 13px;
+  cursor: pointer;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  /* PERF-016: Specific transition properties instead of 'all' to avoid animating layout-triggering properties */
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tool-button:hover {
+  background-color: var(--button-hover);
+}
+
+.tool-button:active {
+  background-color: var(--button-active);
+}
+
+.tool-button:disabled,
+.tool-button[aria-disabled="true"] {
+  cursor: not-allowed;
+  opacity: 0.5;
+}
+
+.tool-button i {
+  font-size: 15px;
+}
+
+.tool-button.is-active,
+.tool-button.is-active:hover {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: rgba(3, 102, 214, 0.08);
+}
+
+.btn-text {
+  display: none;
+}
+
+.toolbar .tool-button {
+  height: 28px;
+  min-width: 28px;
+}
+
+.toolbar .tool-button.sync-active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+}
+
+.file-input {
+  display: none;
+}
+
+/* Drag overlay: full-screen drop target shown when user drags a file over the window */
+.drag-overlay {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 9999;
+  background-color: rgba(0, 0, 0, 0.45);
+  pointer-events: none;
+  align-items: center;
+  justify-content: center;
+}
+
+.drag-overlay.active {
+  display: flex;
+  pointer-events: auto;
+}
+
+.drag-overlay-inner {
+  border: 3px dashed var(--accent-color);
+  border-radius: 12px;
+  padding: 48px 64px;
+  text-align: center;
+  color: #ffffff;
+  background-color: rgba(3, 102, 214, 0.15);
+  animation: overlayPulse 1.4s ease-in-out infinite;
+}
+
+.drag-overlay-icon {
+  display: block;
+  font-size: 3rem;
+  margin-bottom: 12px;
+  color: var(--accent-color);
+}
+
+.drag-overlay-text {
+  font-size: 1.4rem;
+  font-weight: 600;
+  margin-bottom: 4px;
+}
+
+.drag-overlay-sub {
+  font-size: 0.85rem;
+  opacity: 0.75;
+  margin-bottom: 0;
+}
+
+@keyframes overlayPulse {
+  0%, 100% { transform: scale(1); }
+  50% { transform: scale(1.015); }
+}
+
+/* Editor drop hint: subtle text at bottom of editor pane, shown only when empty */
+.drop-hint {
+  position: absolute;
+  bottom: 14px;
+  left: 0;
+  right: 0;
+  text-align: center;
+  font-size: 0.75rem;
+  color: var(--text-color);
+  opacity: 0.35;
+  pointer-events: none;
+  user-select: none;
+  z-index: 3;
+}
+
+.editor-pane:has(#markdown-editor:not(:placeholder-shown)) .drop-hint {
+  display: none;
+}
+
+.line-numbers {
+  position: absolute;
+  top: 20px;
+  bottom: 20px;
+  left: 20px;
+  width: var(--line-number-gutter);
+  padding: 10px 8px 10px 0;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  text-align: right;
+  color: var(--text-secondary);
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  box-sizing: border-box;
+  overflow: hidden;
+  pointer-events: none;
+  user-select: none;
+  z-index: 2;
+  font-variant-numeric: tabular-nums;
+}
+
+.line-numbers .line-number {
+  display: block;
+  height: auto;
+}
+
+.editor-highlight-layer {
+  position: absolute;
+  inset: 20px 0 20px calc(20px + var(--line-number-gutter));
+  padding: 10px;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+  color: transparent;
+  pointer-events: none;
+  overflow: auto;
+  background-color: var(--editor-bg);
+  border-radius: 4px;
+  z-index: 1;
+}
+
+.editor-highlight-layer::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-thumb {
+  background: transparent;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+.find-highlight {
+  background-color: var(--fr-match-highlight, rgba(255, 223, 93, 0.4)) !important;
+  border-radius: 2px;
+  color: transparent !important;
+  padding: 0 !important;
+  margin: 0 !important;
+}
+
+.find-highlight.active {
+  background-color: var(--fr-match-active, #ff9b30) !important;
+  color: transparent !important;
+  padding: 0 !important;
+  margin: 0 !important;
+  outline: 1px solid var(--accent-color, #0366d6) !important;
+  outline-offset: -1px;
+}
+
+.preview-find-highlight {
+  background-color: var(--fr-match-highlight, rgba(255, 223, 93, 0.4)) !important;
+  color: var(--fr-match-text-color, inherit) !important;
+  border-radius: 2px;
+  padding: 0 1px !important;
+  margin: 0 !important;
+}
+
+.preview-find-highlight.active {
+  background-color: var(--fr-match-active, #ff9b30) !important;
+  color: var(--fr-match-active-text-color, inherit) !important;
+  outline: 1px solid var(--accent-color, #0366d6) !important;
+  outline-offset: -1px;
+}
+
+/* Dropdown improvements */
+.dropdown-menu {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+}
+
+.dropdown-item {
+  color: var(--text-color);
+}
+
+.dropdown-item:hover, .dropdown-item:focus {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+/* Markdown formatting toolbar */
+.markdown-format-toolbar {
+  display: flex;
+  align-items: center;
+  height: 34px;
+  padding: 0 6px;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  overflow-x: auto;
+  overflow-y: hidden;
+  flex-shrink: 0;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.markdown-format-toolbar::-webkit-scrollbar {
+  display: none;
+}
+
+.markdown-toolbar-group {
+  display: flex;
+  align-items: center;
+  gap: 2px;
+  height: 100%;
+  padding: 0 6px;
+  border-right: 1px solid var(--border-color);
+  flex-shrink: 0;
+}
+
+.markdown-toolbar-group:first-child {
+  padding-left: 0;
+}
+
+.markdown-toolbar-group:last-child {
+  border-right: none;
+  padding-right: 0;
+}
+
+.markdown-tool-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 26px;
+  height: 26px;
+  border: 1px solid transparent;
+  border-radius: 4px;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 14px;
+  line-height: 1;
+  padding: 0;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.markdown-tool-btn:hover,
+.markdown-tool-btn:focus-visible {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+}
+
+.markdown-tool-btn:active {
+  background-color: var(--button-active);
+}
+
+.markdown-tool-btn:disabled,
+.markdown-tool-btn.disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+  pointer-events: none;
+}
+
+.markdown-tool-btn i {
+  font-size: 15px;
+}
+
+.markdown-tool-btn[data-md-action="reference"] i::before {
+  content: "[ ]";
+  font-style: normal;
+  font-size: 12px;
+  letter-spacing: -0.12em;
+}
+
+.markdown-tool-btn.text-tool {
+  width: auto;
+  min-width: 26px;
+  padding: 0 5px;
+  font-weight: 600;
+  font-family: Georgia, "Times New Roman", serif;
+}
+
+.heading-group .markdown-tool-btn {
+  min-width: 30px;
+}
+
+
+
+/* Loading indicators */
+.loading {
+  opacity: 0.6;
+  pointer-events: none;
+}
+
+/* Focus outline for accessibility */
+button:focus, 
+a:focus {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+/* Animation for copied message */
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+/* Tooltip styles */
+.tooltip {
+  position: absolute;
+  background: var(--button-bg);
+  border: 1px solid var(--border-color);
+  padding: 5px 8px;
+  border-radius: 4px;
+  font-size: 12px;
+  z-index: 1000;
+  animation: fadeIn 0.2s ease;
+}
+
+/* Styles for GitHub markdown preview light mode */
+.markdown-body {
+  color-scheme: light;
+  --color-prettylights-syntax-comment: #6a737d;
+  --color-prettylights-syntax-constant: #005cc5;
+  --color-prettylights-syntax-entity: #6f42c1;
+  --color-prettylights-syntax-storage-modifier-import: #24292e;
+  --color-prettylights-syntax-entity-tag: #22863a;
+  --color-prettylights-syntax-keyword: #cf222e;
+  --color-prettylights-syntax-string: #032f62;
+  --color-prettylights-syntax-variable: #e36209;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #b31d28;
+  --color-prettylights-syntax-invalid-illegal-text: #fafbfc;
+  --color-prettylights-syntax-invalid-illegal-bg: #b31d28;
+  --color-prettylights-syntax-carriage-return-text: #fafbfc;
+  --color-prettylights-syntax-carriage-return-bg: #d73a49;
+  --color-prettylights-syntax-string-regexp: #22863a;
+  --color-prettylights-syntax-markup-list: #735c0f;
+  --color-prettylights-syntax-markup-heading: #005cc5;
+  --color-prettylights-syntax-markup-italic: #24292e;
+  --color-prettylights-syntax-markup-bold: #24292e;
+  --color-prettylights-syntax-markup-deleted-text: #b31d28;
+  --color-prettylights-syntax-markup-deleted-bg: #ffeef0;
+  --color-prettylights-syntax-markup-inserted-text: #22863a;
+  --color-prettylights-syntax-markup-inserted-bg: #f0fff4;
+  --color-prettylights-syntax-markup-changed-text: #e36209;
+  --color-prettylights-syntax-markup-changed-bg: #ffebda;
+  --color-prettylights-syntax-markup-ignored-text: #f6f8fa;
+  --color-prettylights-syntax-markup-ignored-bg: #005cc5;
+  --color-prettylights-syntax-meta-diff-range: #6f42c1;
+  --color-prettylights-syntax-brackethighlighter-angle: #586069;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #e1e4e8;
+  --color-prettylights-syntax-constant-other-reference-link: #032f62;
+  --color-fg-default: #24292e;
+  --color-fg-muted: #586069;
+  --color-fg-subtle: #6a737d;
+  --color-canvas-default: #ffffff;
+  --color-canvas-subtle: #f6f8fa;
+  --color-border-default: #e1e4e8;
+  --color-border-muted: #eaecef;
+  --color-neutral-muted: rgba(175,184,193,0.2);
+  --color-accent-fg: #0366d6;
+  --color-accent-emphasis: #0366d6;
+  --color-attention-subtle: #fff5b1;
+  --color-danger-fg: #d73a49;
+}
+
+/* Styles for GitHub markdown preview dark mode */
+[data-theme="dark"] .markdown-body {
+  color-scheme: dark;
+  --color-prettylights-syntax-comment: #8b949e;
+  --color-prettylights-syntax-constant: #79c0ff;
+  --color-prettylights-syntax-entity: #d2a8ff;
+  --color-prettylights-syntax-storage-modifier-import: #c9d1d9;
+  --color-prettylights-syntax-entity-tag: #7ee787;
+  --color-prettylights-syntax-keyword: #ff7b72;
+  --color-prettylights-syntax-string: #a5d6ff;
+  --color-prettylights-syntax-variable: #ffa657;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #f85149;
+  --color-prettylights-syntax-invalid-illegal-text: #f0f6fc;
+  --color-prettylights-syntax-invalid-illegal-bg: #8e1519;
+  --color-prettylights-syntax-carriage-return-text: #f0f6fc;
+  --color-prettylights-syntax-carriage-return-bg: #b62324;
+  --color-prettylights-syntax-string-regexp: #7ee787;
+  --color-prettylights-syntax-markup-list: #f2cc60;
+  --color-prettylights-syntax-markup-heading: #1f6feb;
+  --color-prettylights-syntax-markup-italic: #c9d1d9;
+  --color-prettylights-syntax-markup-bold: #c9d1d9;
+  --color-prettylights-syntax-markup-deleted-text: #ffdcd7;
+  --color-prettylights-syntax-markup-deleted-bg: #67060c;
+  --color-prettylights-syntax-markup-inserted-text: #aff5b4;
+  --color-prettylights-syntax-markup-inserted-bg: #033a16;
+  --color-prettylights-syntax-markup-changed-text: #ffdfb6;
+  --color-prettylights-syntax-markup-changed-bg: #5a1e02;
+  --color-prettylights-syntax-markup-ignored-text: #c9d1d9;
+  --color-prettylights-syntax-markup-ignored-bg: #1158c7;
+  --color-prettylights-syntax-meta-diff-range: #d2a8ff;
+  --color-prettylights-syntax-brackethighlighter-angle: #8b949e;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #484f58;
+  --color-prettylights-syntax-constant-other-reference-link: #a5d6ff;
+  --color-fg-default: #c9d1d9;
+  --color-fg-muted: #8b949e;
+  --color-fg-subtle: #484f58;
+  --color-canvas-default: #0d1117;
+  --color-canvas-subtle: #161b22;
+  --color-border-default: #30363d;
+  --color-border-muted: #21262d;
+  --color-neutral-muted: rgba(110,118,129,0.4);
+  --color-accent-fg: #58a6ff;
+  --color-accent-emphasis: #1f6feb;
+  --color-attention-subtle: rgba(187,128,9,0.15);
+  --color-danger-fg: #f85149;
+}
+
+/* Override specific styles for dark mode tables and code */
+[data-theme="dark"] .markdown-body table tr {
+  background-color: var(--table-bg);
+}
+
+[data-theme="dark"] .markdown-body table tr:nth-child(2n) {
+  background-color: #1c2128; /* Slightly lighter than base dark background */
+}
+
+[data-theme="dark"] .markdown-body pre {
+  background-color: var(--code-bg);
+}
+
+[data-theme="dark"] .markdown-body code {
+  background-color: var(--code-bg);
+}
+
+/* Syntax Highlighting Mapping to GitHub Variables */
+.hljs {
+  color: var(--color-fg-default);
+}
+.hljs-doctag,
+.hljs-keyword,
+.hljs-meta .hljs-keyword,
+.hljs-template-tag,
+.hljs-template-variable,
+.hljs-type,
+.hljs-variable.language_ {
+  color: var(--color-prettylights-syntax-keyword);
+}
+.hljs-title,
+.hljs-title.class_,
+.hljs-title.class_.inherited__,
+.hljs-title.function_ {
+  color: var(--color-prettylights-syntax-entity);
+}
+.hljs-attr,
+.hljs-attribute,
+.hljs-literal,
+.hljs-meta,
+.hljs-number,
+.hljs-operator,
+.hljs-variable,
+.hljs-selector-attr,
+.hljs-selector-class,
+.hljs-selector-id {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-regexp,
+.hljs-string,
+.hljs-meta .hljs-string {
+  color: var(--color-prettylights-syntax-string);
+}
+.hljs-built_in,
+.hljs-symbol {
+  color: var(--color-prettylights-syntax-variable);
+}
+.hljs-comment,
+.hljs-code,
+.hljs-formula {
+  color: var(--color-prettylights-syntax-comment);
+}
+.hljs-name,
+.hljs-quote,
+.hljs-selector-tag,
+.hljs-selector-pseudo {
+  color: var(--color-prettylights-syntax-entity-tag);
+}
+.hljs-subst {
+  color: var(--color-fg-default);
+}
+.hljs-section {
+  color: var(--color-prettylights-syntax-markup-heading);
+  font-weight: bold;
+}
+.hljs-bullet {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-emphasis {
+  color: var(--color-fg-default);
+  font-style: italic;
+}
+.hljs-strong {
+  color: var(--color-fg-default);
+  font-weight: bold;
+}
+.hljs-addition {
+  color: var(--color-prettylights-syntax-markup-inserted-text);
+  background-color: var(--color-prettylights-syntax-markup-inserted-bg);
+}
+.hljs-deletion {
+  color: var(--color-prettylights-syntax-markup-deleted-text);
+  background-color: var(--color-prettylights-syntax-markup-deleted-bg);
+}
+
+.stats-container {
+  font-size: 0.8rem;
+  color: var(--text-color);
+}
+
+.stat-item {
+  align-items: center;
+}
+
+.stat-item i {
+  font-size: 0.9rem;
+  opacity: 0.8;
+}
+
+#importDropdown,
+#exportDropdown,
+#languageDropdown {
+  font-size: 0.8rem;
+}
+
+#importDropdown i,
+#exportDropdown i,
+#languageDropdown i {
+  font-size: 0.9rem;
+}
+
+/* Ensure desktop dropdown menu options match the stats-container font size */
+[aria-labelledby="importDropdown"] .dropdown-item,
+[aria-labelledby="exportDropdown"] .dropdown-item,
+[aria-labelledby="languageDropdown"] .dropdown-item {
+  font-size: 0.8rem;
+}
+
+/* Ensure mobile menu import, export, and language dropdown triggers/options match the mobile stats-container font size */
+#mobile-import-button,
+#mobile-import-github-button,
+#mobile-export-md,
+#mobile-export-html,
+#mobile-export-pdf,
+#mobileLanguageDropdown {
+  font-size: 0.9rem !important;
+}
+
+[aria-labelledby="mobileLanguageDropdown"] .dropdown-item {
+  font-size: 0.9rem;
+}
+
+.editor-pane {
+  overflow: hidden;
+}
+
+/* Mobile Menu Styles */
+.mobile-menu {
+  display: none;
+  position: relative;
+  z-index: 1001;
+}
+
+
+
+/* slide‑in panel */
+.mobile-menu-panel {
+  position: fixed;
+  top: 0;
+  right: -300px;
+  width: 280px;
+  height: 100vh;
+  background-color: var(--bg-color);
+  box-shadow: -2px 0 10px rgba(0, 0, 0, 0.2);
+  transition: right 0.3s ease;
+  overflow-y: auto;
+  padding: 1rem;
+  display: flex;
+  flex-direction: column;
+  z-index: 1002;
+}
+
+.mobile-menu-panel.active {
+  right: 0;
+}
+
+/* translucent overlay behind panel */
+.mobile-menu-overlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100vh;
+  background-color: rgba(0, 0, 0, 0.5);
+  opacity: 0;
+  visibility: hidden;
+  pointer-events: none;
+  transition: opacity 0.3s ease, visibility 0.3s ease;
+  z-index: 1000;
+}
+
+.mobile-menu-overlay.active {
+  opacity: 1;
+  visibility: visible;
+  pointer-events: auto;
+}
+
+/* header inside mobile menu */
+.mobile-menu-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 1rem;
+}
+
+.mobile-menu-header h5 {
+  margin: 0;
+  font-size: 1.25rem;
+  color: var(--text-color);
+}
+
+/* stats section in mobile menu */
+.mobile-stats-container {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+  margin-bottom: 1rem;
+}
+
+.mobile-stats-container .stat-item {
+  font-size: 0.9rem;
+  color: var(--text-color);
+  display: flex;
+  align-items: center;
+}
+
+.mobile-stats-container .stat-item i {
+  margin-right: 0.5em;
+  opacity: 0.8;
+}
+
+/* menu buttons list */
+.mobile-menu-items {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  flex-grow: 1;
+}
+
+/* each menu item */
+.mobile-menu-item {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 6px;
+  padding: 0.6rem 1rem;
+  font-size: 1rem;
+  text-align: left;
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  transition: background-color 0.2s ease;
+  cursor: pointer;
+}
+
+.mobile-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-menu-item:active {
+  background-color: var(--button-active);
+}
+
+/* close button override */
+#close-mobile-menu.tool-button {
+  padding: 0.25rem 0.5rem;
+  font-size: 1rem;
+}
+
+/* Mobile document tabs section */
+.mobile-tabs-section {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-tabs-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 0.5rem;
+}
+
+.mobile-tabs-label {
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--text-color);
+  opacity: 0.8;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+.mobile-new-tab-btn {
+  background: none;
+  border: 1px solid var(--border-color);
+  border-radius: 4px;
+  color: var(--text-color);
+  padding: 2px 7px;
+  font-size: 0.9rem;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.15s ease;
+}
+
+.mobile-new-tab-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-list {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  max-height: 180px;
+  overflow-y: auto;
+}
+
+.mobile-tab-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  padding: 0.45rem 0.75rem;
+  font-size: 0.9rem;
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+  gap: 0.5rem;
+}
+
+.mobile-tab-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-item.active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: var(--bg-color);
+}
+
+.mobile-tab-title {
+  flex: 1;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  min-width: 0;
+}
+
+.mobile-tab-item .tab-menu-btn {
+  opacity: 0.6;
+}
+
+.mobile-tab-item:hover .tab-menu-btn,
+.mobile-tab-item.active .tab-menu-btn {
+  opacity: 0.8;
+}
+
+#mobile-tab-reset-btn {
+  margin-left: 0;
+  height: auto;
+  padding: 0.45rem 0.75rem;
+  justify-content: center;
+  font-size: 0.9rem;
+}
+
+/* ==========================================
+   NAVBAR RESPONSIVE BREAKPOINTS
+   >= 1080px : full desktop navbar
+   <  1080px : mobile hamburger + stacked panes
+   ========================================== */
+
+/* Mobile / tablet (< 1080px): switch to hamburger, stack panes */
+@media (max-width: 1079px) {
+  /* Override Bootstrap d-md-flex / d-md-none so the breakpoint is 1080px */
+  .stats-container,
+  .toolbar {
+    display: none !important;
+  }
+
+  /* Expand touch target sizes to meet WCAG mobile guidelines */
+  .markdown-tool-btn {
+    width: 36px !important;
+    height: 36px !important;
+    font-size: 16px !important;
+  }
+  .markdown-format-toolbar {
+    height: 44px !important;
+  }
+  .tab-close-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+  .tab-menu-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+
+  .mobile-menu {
+    display: block !important;
+  }
+
+  /* Stack editor and preview vertically */
+  .content-container {
+    flex-direction: column;
+  }
+
+  .editor-pane,
+  .preview-pane {
+    flex: none;
+    height: 50%;
+    border-right: none;
+  }
+
+  .editor-pane {
+    border-bottom: 1px solid var(--border-color);
+  }
+
+  /* Hide drag-resize divider (touch devices don't use it) */
+  .resize-divider {
+    display: none;
+  }
+
+  /* Single-pane view modes: occupy full height */
+  .content-container.view-editor-only .editor-pane,
+  .content-container.view-preview-only .preview-pane {
+    height: 100%;
+  }
+
+  .content-container.view-split .editor-pane,
+  .content-container.view-split .preview-pane {
+    height: 50%;
+  }
+}
+
+.github-link {
+  color: var(--text-color);
+  text-decoration: none;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: transform 0.2s ease, color 0.2s ease;
+  margin-right: 2rem;
+}
+
+.github-link:hover {
+  color: var(--accent-color);
+  transform: scale(1.1);
+}
+
+.github-link i {
+  font-size: 1.25rem;
+}
+
+/* ========================================
+   HEADER LAYOUT
+   ======================================== */
+.header-container {
+  position: relative;
+  min-height: 30px;
+}
+
+.app-header h1 {
+  font-size: 1.05rem;
+  line-height: 1.1;
+}
+
+.header-left {
+  flex: 1 0 auto;
+  justify-content: flex-start;
+  white-space: nowrap;
+}
+
+.header-right {
+  flex: 1 0 auto;
+  justify-content: flex-end;
+  white-space: nowrap;
+}
+
+/* Pane View States */
+.content-container.view-editor-only .preview-pane {
+  display: none;
+}
+
+.content-container.view-editor-only .editor-pane {
+  flex: 1;
+  border-right: none;
+}
+
+.content-container.view-preview-only .editor-pane {
+  display: none;
+}
+
+.content-container.view-preview-only .preview-pane {
+  flex: 1;
+}
+
+.content-container.view-split .editor-pane,
+.content-container.view-split .preview-pane {
+  flex: 1;
+}
+
+/* Compact desktop (< 1280px): compact toolbar */
+@media (max-width: 1280px) {
+  /* Compact toolbar at medium widths */
+  .toolbar {
+    gap: 4px;
+  }
+}
+
+
+
+/* ========================================
+   RESIZE DIVIDER - Story 1.3
+   ======================================== */
+
+.resize-divider {
+  width: 8px;
+  background-color: transparent;
+  cursor: col-resize;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+  position: relative;
+  z-index: 10;
+  transition: background-color 0.2s ease;
+}
+
+.resize-divider:hover {
+  background-color: var(--button-hover);
+}
+
+.resize-divider.dragging {
+  background-color: var(--accent-color);
+}
+
+.resize-divider-handle {
+  width: 2px;
+  height: 40px;
+  background-color: var(--border-color);
+  border-radius: 2px;
+  transition: background-color 0.2s ease, width 0.2s ease;
+}
+
+.resize-divider:hover .resize-divider-handle,
+.resize-divider.dragging .resize-divider-handle {
+  background-color: var(--accent-color);
+  width: 3px;
+}
+
+/* Hide divider in single-pane modes */
+.content-container.view-editor-only .resize-divider,
+.content-container.view-preview-only .resize-divider {
+  display: none;
+}
+
+
+
+/* Prevent text selection during drag */
+.resizing {
+  user-select: none;
+  cursor: col-resize !important;
+}
+
+.resizing * {
+  cursor: col-resize !important;
+}
+
+.resizing #markdown-preview,
+.resizing #markdown-editor,
+.resizing .line-numbers {
+  pointer-events: none !important;
+}
+
+/* ========================================
+   MOBILE VIEW MODE CONTROLS - Story 1.4
+   ======================================== */
+
+.mobile-view-mode-group {
+  display: flex;
+  gap: 0;
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-view-mode-btn {
+  flex: 1;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  padding: 8px 12px;
+  font-size: 14px;
+  cursor: pointer;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  transition: all 0.2s ease;
+}
+
+.mobile-view-mode-btn:first-child {
+  border-radius: 6px 0 0 6px;
+}
+
+.mobile-view-mode-btn:last-child {
+  border-radius: 0 6px 6px 0;
+}
+
+.mobile-view-mode-btn:not(:last-child) {
+  border-right: none;
+}
+
+.mobile-view-mode-btn:hover,
+.mobile-view-mode-btn:active {
+  background-color: var(--button-hover);
+}
+
+.mobile-view-mode-btn.active {
+  background-color: var(--button-bg);
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  border-width: 2px;
+  padding: 7px 11px;
+}
+
+.mobile-view-mode-btn.active:not(:last-child) {
+  border-right: 2px solid var(--accent-color);
+}
+
+.mobile-view-mode-btn i {
+  font-size: 18px;
+}
+
+.mobile-view-mode-btn span {
+  font-size: 12px;
+}
+
+/* ========================================
+   RESPONSIVE VIEW MODE FIXES - Story 1.5
+   ======================================== */
+
+
+
+/* ========================================
+   PDF EXPORT TABLE FIX - Rowspan/Colspan
+   ======================================== */
+
+/* Fix for html2canvas not properly rendering rowspan/colspan cells.
+   Apply backgrounds to cells instead of rows to prevent row backgrounds
+   from painting over rowspan cells during canvas capture. */
+.pdf-export table tr {
+  background-color: transparent !important;
+}
+
+.pdf-export table th,
+.pdf-export table td {
+  background-color: var(--table-bg, #ffffff);
+  position: relative;
+}
+
+.pdf-export table tr:nth-child(2n) th,
+.pdf-export table tr:nth-child(2n) td {
+  background-color: var(--bg-color, #f6f8fa);
+}
+
+/* Ensure rowspan cells render correctly */
+.pdf-export table th[rowspan],
+.pdf-export table td[rowspan] {
+  vertical-align: middle;
+  background-color: var(--table-bg, #ffffff) !important;
+}
+
+/* Ensure colspan cells render correctly */
+.pdf-export table th[colspan],
+.pdf-export table td[colspan] {
+  text-align: center;
+}
+
+/* Dark mode PDF export table fix */
+[data-theme="dark"] .pdf-export table th,
+[data-theme="dark"] .pdf-export table td {
+  background-color: var(--table-bg, #161b22);
+}
+
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) th,
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) td {
+  background-color: #1c2128;
+}
+
+[data-theme="dark"] .pdf-export table th[rowspan],
+[data-theme="dark"] .pdf-export table td[rowspan] {
+  background-color: var(--table-bg, #161b22) !important;
+}
+
+/* ========================================
+   MERMAID DIAGRAM TOOLBAR
+   ======================================== */
+
+.mermaid-container {
+  position: relative;
+}
+
+.mermaid-toolbar {
+  position: absolute;
+  top: 8px;
+  right: 8px;
+  display: flex;
+  gap: 4px;
+  opacity: 0;
+  transition: opacity 0.2s ease;
+  z-index: 10;
+}
+
+.mermaid-container:hover .mermaid-toolbar {
+  opacity: 1;
+}
+
+.mermaid-toolbar-btn {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 4px;
+  padding: 4px 7px;
+  font-size: 13px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  gap: 3px;
+  transition: background-color 0.2s ease, color 0.2s ease;
+  white-space: nowrap;
+}
+
+.mermaid-toolbar-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--accent-color);
+}
+
+.mermaid-toolbar-btn:active {
+  background-color: var(--button-active);
+}
+
+.mermaid-toolbar-btn i {
+  font-size: 14px;
+}
+
+/* ========================================
+   MERMAID ZOOM MODAL
+   ======================================== */
+
+#mermaid-zoom-modal {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 2000;
+  background-color: rgba(0, 0, 0, 0.75);
+  align-items: center;
+  justify-content: center;
+}
+
+#mermaid-zoom-modal.active {
+  display: flex;
+}
+
+.mermaid-modal-content {
+  background-color: var(--bg-color);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  padding: 16px;
+  width: 85vw;
+  height: 85vh;
+  max-width: 85vw;
+  max-height: 85vh;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+@media (max-width: 576px) {
+  .mermaid-modal-content {
+    width: 95vw;
+    height: 90vh;
+    max-width: 95vw;
+    max-height: 90vh;
+    padding: 10px;
+  }
+}
+
+.mermaid-modal-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.mermaid-modal-header span {
+  font-weight: 600;
+  font-size: 15px;
+  color: var(--text-color);
+}
+
+.mermaid-modal-close {
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 1.2rem;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.2s ease;
+}
+
+.mermaid-modal-close:hover {
+  background-color: var(--button-hover);
+}
+
+.mermaid-modal-diagram {
+  overflow: auto;
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 200px;
+  cursor: grab;
+}
+
+.mermaid-modal-diagram.dragging {
+  cursor: grabbing;
+}
+
+.mermaid-modal-diagram svg {
+  transform-origin: center;
+  transition: transform 0.1s ease;
+  max-width: none;
+}
+
+.mermaid-modal-controls {
+  display: flex;
+  justify-content: center;
+  gap: 8px;
+  flex-wrap: wrap;
+}
+
+.mermaid-modal-controls .mermaid-toolbar-btn {
+  opacity: 1;
+}
+
+/* ========================================
+   DOCUMENT TABS & SESSION MANAGEMENT
+   ======================================== */
+
+.tab-bar {
+  display: flex;
+  align-items: center;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  height: 32px;
+  overflow: visible;  /* ← was: overflow: hidden */
+  flex-shrink: 0;
+  padding: 0 4px;
+  gap: 0;
+  user-select: none;
+  position: relative;
+  z-index: 10;
+}
+
+.tab-list {
+  display: flex;
+  align-items: flex-end;
+  overflow-x: auto;
+  overflow-y: visible;  /* ← was: overflow-y: hidden */
+  flex: 1;
+  height: 100%;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.tab-list::-webkit-scrollbar {
+  display: none;
+}
+
+.tab-item {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  height: 32px;
+  padding: 0 8px 0 10px;
+  min-width: 100px;
+  max-width: 180px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-bottom: 1px solid transparent;
+  border-radius: 6px 6px 0 0;
+  cursor: pointer;
+  font-size: 13px;
+  color: var(--text-color);
+  white-space: nowrap;
+  /* overflow: hidden; <-- REMOVE THIS */
+  position: relative;
+  transition: background-color 0.15s ease, color 0.15s ease;
+  flex-shrink: 0;
+  margin-right: 2px;
+  opacity: 0.7;
+}
+
+.tab-item:hover {
+  background-color: var(--button-hover);
+  opacity: 0.9;
+}
+
+.tab-item.active {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+  border-bottom: 1px solid var(--bg-color);
+  opacity: 1;
+  z-index: 2;
+}
+
+.tab-item.unsaved::after {
+  content: '';
+  display: inline-block;
+  width: 6px;
+  height: 6px;
+  background-color: var(--accent-color);
+  border-radius: 50%;
+  flex-shrink: 0;
+  margin-left: 2px;
+}
+
+.tab-title {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  flex: 1;
+  min-width: 0;
+}
+
+.tab-close-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 16px;
+  height: 16px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 11px;
+  opacity: 0;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+}
+
+.tab-item:hover .tab-close-btn,
+.tab-item.active .tab-close-btn {
+  opacity: 0.6;
+}
+
+.tab-close-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-new-btn {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  height: 24px;
+  padding: 0 8px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 12px;
+  flex-shrink: 0;
+  margin-left: 6px;
+  align-self: center;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tab-new-btn:hover {
+  background-color: rgba(46, 160, 67, 0.1);
+  border-color: var(--accent-color, #2ea043);
+  color: var(--accent-color, #2ea043);
+}
+
+.tab-new-btn:active {
+  background-color: rgba(46, 160, 67, 0.2);
+}
+
+/* Drag-and-drop visual feedback */
+.tab-item.dragging {
+  opacity: 0.4;
+}
+
+.tab-item.drag-over {
+  border-left: 2px solid var(--accent-color);
+}
+
+/* Tab enter animation */
+@keyframes tabSlideIn {
+  from { opacity: 0; transform: translateY(4px); }
+  to   { opacity: 0.7; transform: translateY(0); }
+}
+
+.tab-item {
+  animation: tabSlideIn 0.12s ease forwards;
+}
+
+.tab-item.active {
+  animation: none;
+}
+
+/* Hide tab bar on very small screens — single-file use */
+@media (max-width: 480px) {
+  .tab-bar {
+    display: none;
+  }
+}
+
+/* ========================================
+   TAB OVERFLOW — Scroll Buttons & Fade Indicators
+   ======================================== */
+
+.tab-scroll-btn {
+  display: none;
+  align-items: center;
+  justify-content: center;
+  width: 24px;
+  height: 24px;
+  border-radius: 4px;
+  background: none;
+  border: 1px solid transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 14px;
+  flex-shrink: 0;
+  padding: 0;
+  transition: background-color 0.15s ease, border-color 0.15s ease, opacity 0.15s ease;
+  z-index: 2;
+  opacity: 0.6;
+}
+
+.tab-scroll-btn:hover {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+  opacity: 1;
+}
+
+.tab-scroll-btn:active {
+  background-color: var(--button-active);
+}
+
+/* Show scroll buttons only when overflow exists */
+.tab-bar.has-overflow-left .tab-scroll-left,
+.tab-bar.has-overflow-right .tab-scroll-right {
+  display: flex;
+}
+
+/* Overflow fade indicators — subtle gradient at clipped edges */
+.tab-list::before,
+.tab-list::after {
+  content: '';
+  position: sticky;
+  top: 0;
+  bottom: 0;
+  width: 0;
+  flex-shrink: 0;
+  pointer-events: none;
+  z-index: 3;
+  transition: box-shadow 0.2s ease;
+}
+
+.tab-list::before {
+  left: 0;
+}
+
+.tab-list::after {
+  right: 0;
+}
+
+.tab-bar.has-overflow-left .tab-list::before {
+  box-shadow: 8px 0 12px -4px rgba(0, 0, 0, 0.12);
+}
+
+.tab-bar.has-overflow-right .tab-list::after {
+  box-shadow: -8px 0 12px -4px rgba(0, 0, 0, 0.12);
+}
+
+[data-theme="dark"] .tab-bar.has-overflow-left .tab-list::before {
+  box-shadow: 8px 0 12px -4px rgba(0, 0, 0, 0.35);
+}
+
+[data-theme="dark"] .tab-bar.has-overflow-right .tab-list::after {
+  box-shadow: -8px 0 12px -4px rgba(0, 0, 0, 0.35);
+}
+
+/* ========================================
+   THREE-DOT TAB MENU
+   ======================================== */
+
+.tab-menu-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 22px;
+  height: 22px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 14px;
+  font-weight: bold;
+  letter-spacing: 1px;
+  opacity: 0.65;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+  position: relative;
+}
+
+/* Touch Hitbox Expansion for Tab Menu Button */
+.tab-menu-btn::before {
+  content: '';
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  width: 48px;
+  height: 48px;
+}
+
+/* Touch-optimized styling for coarser pointers (e.g., smartphones & tablets) */
+@media (pointer: coarse) {
+  .tab-bar {
+    height: 40px !important;
+  }
+  .tab-item {
+    height: 40px !important;
+    font-size: 14px !important;
+    padding: 0 10px 0 12px !important;
+    gap: 8px !important;
+  }
+  .tab-new-btn,
+  .tab-reset-btn {
+    height: 32px !important;
+    font-size: 14px !important;
+    padding: 0 12px !important;
+  }
+  .tab-scroll-btn {
+    width: 32px !important;
+    height: 32px !important;
+    font-size: 18px !important;
+  }
+  .tab-menu-btn {
+    width: 30px !important;
+    height: 30px !important;
+    font-size: 18px !important;
+  }
+  .tab-close-btn {
+    width: 20px !important;
+    height: 20px !important;
+    font-size: 13px !important;
+    opacity: 0.8 !important;
+  }
+}
+
+.tab-item:hover .tab-menu-btn,
+.tab-item.active .tab-menu-btn {
+  opacity: 0.65;
+}
+
+.tab-menu-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+}
+
+.tab-menu-dropdown {
+  display: none;
+  position: fixed;
+  min-width: 130px;
+  background-color: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
+  z-index: 99999;
+  overflow: hidden;
+  flex-direction: column;
+}
+
+.tab-menu-dropdown.open {
+  display: flex;
+}
+
+.tab-menu-item {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  padding: 7px 12px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  text-align: left;
+  transition: background-color 0.12s ease;
+  white-space: nowrap;
+}
+
+.tab-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.tab-menu-item-danger {
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-menu-item-danger:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+}
+
+/* ========================================
+   RESET BUTTON
+   ======================================== */
+
+.tab-reset-btn {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  height: 24px;
+  padding: 0 8px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 12px;
+  flex-shrink: 0;
+  margin-left: 6px;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tab-reset-btn:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: var(--color-danger-fg, #d73a49);
+}
+
+/* ========================================
+   RESET & RENAME CONFIRMATION MODALS
+   ======================================== */
+
+.reset-modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.45);
+  z-index: 2000;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.reset-modal-overlay.modal-overlay {
+  opacity: 0;
+  visibility: hidden;
+  transition: opacity 0.2s ease, visibility 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible {
+  opacity: 1;
+  visibility: visible;
+}
+
+.reset-modal-box {
+  background: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 24px 28px;
+  min-width: 280px;
+  max-width: 360px;
+  box-shadow: 0 8px 32px rgba(0,0,0,0.25);
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+}
+
+.modal-box {
+  max-height: min(85vh, 760px);
+  opacity: 0;
+  transform: translateY(8px);
+  transition: transform 0.2s ease, opacity 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible .modal-box {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+.modal-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.modal-header .reset-modal-message {
+  text-align: left;
+  flex: 1;
+}
+
+.modal-close-btn {
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  border-radius: 6px;
+  width: 28px;
+  height: 28px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.modal-close-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.modal-body {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(60vh, 520px);
+  overflow: auto;
+  padding-right: 4px;
+}
+
+.modal-section {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.modal-section-title {
+  margin: 0;
+  font-size: 0.95rem;
+  font-weight: 600;
+}
+
+.modal-list {
+  margin: 0;
+  padding-left: 1.1rem;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  font-size: 0.85rem;
+}
+
+.modal-list a {
+  color: var(--accent-color);
+  text-decoration: none;
+}
+
+.modal-list a:hover {
+  text-decoration: underline;
+}
+
+.modal-subtext {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  line-height: 1.4;
+}
+
+.find-replace-meta {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.find-replace-nav {
+  display: inline-flex;
+  gap: 6px;
+}
+
+.find-nav-btn {
+  width: 28px;
+  height: 28px;
+  padding: 0;
+}
+
+.about-header {
+  display: flex;
+  align-items: center;
+  gap: 16px;
+  flex-wrap: wrap;
+}
+
+.about-logo {
+  width: 64px;
+  height: 64px;
+  border-radius: 12px;
+  border: 1px solid var(--border-color);
+  object-fit: cover;
+}
+
+.about-details {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.about-title {
+  margin: 0;
+  font-size: 1.05rem;
+  font-weight: 600;
+}
+
+.about-description {
+  margin: 0;
+  font-size: 0.85rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.about-meta {
+  margin: 0;
+  font-size: 0.78rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.modal-body kbd {
+  padding: 2px 6px;
+  border-radius: 4px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  font-size: 0.75rem;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+}
+
+.reset-modal-box--wide {
+  width: min(92vw, 640px);
+  max-width: 640px;
+}
+
+.reset-modal-message {
+  margin: 0;
+  font-size: 14px;
+  color: var(--text-color);
+  font-weight: 500;
+  text-align: center;
+}
+
+.reset-modal-actions {
+  display: flex;
+  gap: 10px;
+  justify-content: flex-end;
+}
+
+.reset-modal-btn {
+  padding: 6px 16px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  font-size: 13px;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.reset-modal-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.reset-modal-confirm {
+  background-color: var(--color-danger-fg, #d73a49);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: #fff;
+}
+
+.reset-modal-confirm:hover {
+  background-color: #b02a37;
+  border-color: #b02a37;
+}
+
+/* ========================================
+   PDF EXPORT PROGRESS MODAL
+   ======================================== */
+
+.pdf-progress-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 2600;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(0, 0, 0, 0.45);
+  padding: 20px;
+}
+
+.pdf-progress-modal {
+  width: min(92vw, 420px);
+  background: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.28);
+  color: var(--text-color);
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  padding: 20px;
+}
+
+.pdf-progress-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.pdf-progress-title {
+  margin: 0;
+  font-size: 15px;
+  font-weight: 600;
+}
+
+.pdf-progress-percent {
+  font-size: 28px;
+  font-weight: 600;
+  line-height: 1;
+}
+
+.pdf-progress-track {
+  width: 100%;
+  height: 10px;
+  background: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 999px;
+  overflow: hidden;
+}
+
+.pdf-progress-fill {
+  width: 0%;
+  height: 100%;
+  background: var(--accent-color);
+  border-radius: inherit;
+  transition: width 0.18s ease;
+}
+
+.pdf-progress-details {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary);
+}
+
+.pdf-progress-detail {
+  display: flex;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.pdf-progress-detail strong {
+  color: var(--text-color);
+  font-weight: 600;
+}
+
+.pdf-progress-actions {
+  display: flex;
+  justify-content: flex-end;
+}
+
+.tool-button.pdf-export-loading,
+.mobile-menu-item.pdf-export-loading {
+  pointer-events: none;
+}
+/* ========================================
+   RESET MODAL FORM FIELDS
+   ======================================== */
+
+.reset-modal-field {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  text-align: left;
+}
+
+.reset-modal-field-group {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.reset-modal-label {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  font-weight: 600;
+}
+
+.reset-modal-toggle-group {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.reset-modal-option {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 13px;
+  color: var(--text-color);
+}
+
+.reset-modal-option input {
+  margin: 0;
+}
+
+/* ========================================
+   RENAME MODAL INPUT
+   ======================================== */
+
+.rename-modal-input {
+  width: 100%;
+  padding: 7px 10px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  color: var(--text-color);
+  font-size: 13px;
+  outline: none;
+  box-sizing: border-box;
+}
+
+.rename-modal-input:focus {
+  border-color: var(--accent-color);
+}
+
+/* ========================================
+   TOOLBAR POPUP PANELS
+   ======================================== */
+
+.reset-modal-box--xl {
+  width: min(94vw, 980px);
+  max-width: 980px;
+}
+
+.modal-empty {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
+  gap: 12px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px;
+}
+
+.symbol-grid {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px 2px;
+}
+
+.symbol-section-title {
+  margin: 0;
+  font-size: 11px;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--text-secondary, #57606a);
+}
+
+.symbol-section-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+  gap: 12px;
+}
+
+.alert-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
+  gap: 12px;
+  max-height: min(45vh, 360px);
+  overflow: auto;
+  padding: 2px;
+}
+
+.emoji-item,
+.symbol-item,
+.alert-option {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  align-items: center;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 10px;
+  background: var(--bg-color);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
+}
+
+.emoji-item:focus-visible,
+.symbol-item:focus-visible,
+.alert-option:focus-visible {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+.emoji-item.is-selected,
+.symbol-item.is-selected,
+.alert-option.is-selected {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
+  background-color: rgba(88, 166, 255, 0.08);
+}
+
+.emoji-preview {
+  width: 36px;
+  height: 36px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.emoji-preview img {
+  width: 32px;
+  height: 32px;
+}
+
+.emoji-shortcode {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-copy-btn,
+.symbol-copy-btn {
+  border: none;
+  background: transparent;
+  color: var(--text-secondary, #57606a);
+  cursor: pointer;
+  padding: 2px;
+  border-radius: 4px;
+}
+
+.emoji-copy-btn:hover,
+.symbol-copy-btn:hover {
+  color: var(--text-color);
+  background: var(--button-hover);
+}
+
+.emoji-copy-btn.is-copied,
+.symbol-copy-btn.is-copied {
+  color: var(--accent-color);
+}
+
+.symbol-preview {
+  font-size: 28px;
+  line-height: 1;
+}
+
+.symbol-code {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.alert-option {
+  align-items: stretch;
+  text-align: left;
+  padding: 12px;
+}
+
+.alert-preview {
+  margin: 0;
+}
+
+.alert-preview .markdown-alert {
+  padding: 0.5rem 0.9rem;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.alert-preview .markdown-alert-title {
+  margin: 0 0 6px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.alert-preview .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.alert-preview .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.alert-preview .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--text-color);
+}
+
+.alert-preview .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.alert-preview .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.alert-preview .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.alert-preview .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.alert-preview .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-note {
+  color: #4493f8;
+  border-left-color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-tip {
+  color: #3fb950;
+  border-left-color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-important {
+  color: #ab7df8;
+  border-left-color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-warning {
+  color: #d29922;
+  border-left-color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-caution {
+  color: #f85149;
+  border-left-color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+}
+
+.github-import-error {
+  margin: 0;
+  font-size: 12px;
+  color: var(--color-danger-fg, #d73a49);
+  text-align: left;
+  line-height: 1.5;
+}
+
+.github-import-error.is-info {
+  color: var(--text-secondary, #57606a);
+}
+
+#github-import-modal .reset-modal-box {
+  width: 60vw;
+  max-width: 60vw;
+  min-width: 340px;
+  padding: 30px 34px;
+  gap: 16px;
+  box-shadow: 0 20px 48px rgba(0, 0, 0, 0.22);
+}
+
+#github-import-modal .reset-modal-message {
+  font-size: 18px;
+  line-height: 1.35;
+  text-align: left;
+}
+
+#github-import-url,
+#github-import-file-select {
+  min-height: 46px;
+  padding: 10px 12px;
+  font-size: 15px;
+}
+
+#github-import-file-select {
+  min-height: 180px;
+}
+
+.github-import-tree {
+  max-height: 420px;
+  overflow: auto;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 12px;
+  background: var(--bg-color);
+}
+
+.github-import-selection-toolbar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  padding: 10px 12px;
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  background: var(--button-bg);
+}
+
+.github-import-selected-count {
+  font-size: 14px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.github-import-tree ul {
+  list-style: none;
+  margin: 0;
+  padding-left: 18px;
+}
+
+.github-import-tree > ul {
+  padding-left: 4px;
+}
+
+.github-import-tree li {
+  margin: 2px 0;
+}
+
+.github-tree-folder-label {
+  display: inline-block;
+  font-size: 14px;
+  color: var(--text-secondary, #57606a);
+  margin-bottom: 4px;
+}
+
+.github-tree-file-btn {
+  border: 0;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 6px 8px;
+  border-radius: 6px;
+  text-align: left;
+  width: 100%;
+  font-size: 14px;
+}
+
+.github-tree-file-btn:hover,
+.github-tree-file-btn:focus-visible {
+  background: var(--button-hover);
+  outline: none;
+}
+
+.github-tree-file-btn.is-selected {
+  background: rgba(56, 139, 253, 0.14);
+  color: var(--accent-color);
+}
+
+#github-import-modal .reset-modal-actions {
+  gap: 12px;
+}
+
+#github-import-modal .reset-modal-btn {
+  min-height: 42px;
+  padding: 9px 18px;
+  font-size: 14px;
+}
+
+@media (max-width: 576px) {
+  #github-import-modal .reset-modal-box {
+    width: 95vw;
+    max-width: 95vw;
+    min-width: 0;
+    padding: 20px;
+    gap: 14px;
+  }
+
+  .github-import-selection-toolbar {
+    flex-direction: column;
+    align-items: stretch;
+  }
+
+  #github-import-modal .reset-modal-message {
+    font-size: 16px;
+  }
+
+  #github-import-modal .reset-modal-actions {
+    flex-direction: column-reverse;
+  }
+
+  #github-import-modal .reset-modal-btn {
+    width: 100%;
+  }
+}
+
+.frontmatter-table {
+  border-collapse: collapse;
+  margin-bottom: 1.5em;
+  font-size: 0.9em;
+  width: auto;
+  max-width: 100%;
+}
+
+.frontmatter-table th,
+.frontmatter-table td {
+  border: 1px solid var(--border-color);
+  padding: 6px 13px;
+  vertical-align: top;
+  color: var(--text-color);
+}
+
+.frontmatter-table tr:nth-child(odd) th,
+.frontmatter-table tr:nth-child(odd) td {
+  background-color: var(--table-bg);
+}
+
+.frontmatter-table tr:nth-child(even) th,
+.frontmatter-table tr:nth-child(even) td {
+  background-color: var(--editor-bg);
+}
+
+.frontmatter-table th {
+  font-weight: 600;
+  text-align: right;
+  white-space: nowrap;
+  vertical-align: middle;
+}
+
+.frontmatter-table td {
+  text-align: left;
+}
+
+.fm-complex {
+  margin: 0;
+  padding: 4px 6px;
+  font-size: 0.8em;
+  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  white-space: pre-wrap;
+  word-break: break-word;
+  background: transparent;
+  border: none;
+  color: var(--text-color);
+}
+
+.fm-tag {
+  display: inline-block;
+  padding: 2px 8px;
+  margin: 2px 3px 2px 0;
+  border: 1px solid var(--border-color);
+  border-radius: 2em;
+  font-size: 0.8em;
+  font-weight: 500;
+  color: var(--accent-color);
+  background-color: var(--button-bg);
+  white-space: nowrap;
+}
+
+/* ========================================
+   RTL SUPPORT
+   ======================================== */
+
+[dir="rtl"] body {
+  direction: rtl;
+}
+
+[dir="rtl"] .editor-pane {
+  padding-left: 0px;
+  padding-right: 20px;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor,
+[dir="rtl"] .markdown-body {
+  direction: rtl;
+  text-align: right;
+}
+
+[dir="rtl"] .markdown-body pre,
+[dir="rtl"] .markdown-body code,
+[dir="rtl"] .fm-complex {
+  direction: ltr;
+  text-align: left;
+}
+
+[dir="rtl"] .line-numbers {
+  left: auto;
+  right: 20px;
+  padding: 10px 0 10px 8px;
+  text-align: left;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor {
+  padding-left: 10px;
+  padding-right: calc(10px + var(--line-number-gutter));
+}
+
+[dir="rtl"] .editor-highlight-layer {
+  inset: 20px calc(20px + var(--line-number-gutter)) 20px 0;
+}
+
+[dir="rtl"] .mobile-menu-item,
+[dir="rtl"] .tab-menu-item,
+[dir="rtl"] .modal-header .reset-modal-message,
+[dir="rtl"] .reset-modal-field,
+[dir="rtl"] .alert-option,
+[dir="rtl"] .github-import-error,
+[dir="rtl"] #github-import-modal .reset-modal-message,
+[dir="rtl"] .github-tree-file-btn,
+[dir="rtl"] .frontmatter-table td {
+  text-align: right;
+}
+
+[dir="rtl"] .github-import-tree ul {
+  padding-left: 0;
+  padding-right: 18px;
+}
+
+[dir="rtl"] .github-import-tree > ul {
+  padding-right: 4px;
+}
+
+[dir="rtl"] .markdown-body .markdown-alert,
+[dir="rtl"] .alert-preview .markdown-alert {
+  border-left: 0;
+  border-right: 0.25em solid currentColor;
+}
+
+/* ============================================
+   SHARE MODAL
+   ============================================ */
+
+.share-modal-description {
+  font-size: 13px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+}
+
+.share-mode-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.share-mode-card {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 12px 14px;
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  cursor: pointer;
+  transition: border-color 0.15s ease, background-color 0.15s ease;
+  user-select: none;
+}
+
+.share-mode-card:hover {
+  border-color: var(--accent-color);
+  background: var(--button-hover);
+}
+
+.share-mode-card.is-selected {
+  border-color: var(--accent-color);
+  background: color-mix(in srgb, var(--accent-color) 8%, transparent);
+}
+
+.share-mode-card input[type="radio"] {
+  display: none;
+}
+
+.share-card-icon {
+  font-size: 18px;
+  width: 28px;
+  text-align: center;
+  color: var(--text-secondary, #57606a);
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-icon {
+  color: var(--accent-color);
+}
+
+.share-card-body {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  flex: 1;
+  min-width: 0;
+}
+
+.share-card-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.share-card-desc {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.share-card-check {
+  width: 18px;
+  text-align: center;
+  color: var(--accent-color);
+  opacity: 0;
+  transition: opacity 0.15s ease;
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-check {
+  opacity: 1;
+}
+
+.share-url-row {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.share-url-input {
+  flex: 1;
+  font-size: 12px;
+  font-family: var(--font-mono, monospace);
+  color: var(--text-secondary, #57606a);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.share-copy-btn {
+  flex-shrink: 0;
+  padding: 6px 10px;
+}
+
+.share-copy-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.share-modal-notice {
+  font-size: 11px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+  display: flex;
+  align-items: center;
+  gap: 5px;
+}
+
+/* ==========================================================================
+   Multilingual & CJK Optimization styles added by Aegis SEO agency
+   ========================================================================== */
+.lang-select-item {
+  display: flex !important;
+  align-items: center;
+  gap: 8px;
+  cursor: pointer;
+  transition: background-color 0.2s ease, padding-left 0.2s ease;
+}
+
+.lang-select-item:hover {
+  padding-left: 12px;
+}
+
+.lang-select-item.active {
+  background-color: var(--accent-color) !important;
+  color: #ffffff !important;
+  font-weight: 600;
+}
+
+/* Adjust CJK text layout for maximum readability inside the preview pane */
+html[lang="zh"] .markdown-body,
+html[lang="ja"] .markdown-body,
+html[lang="ko"] .markdown-body {
+  line-height: 1.75 !important;
+  letter-spacing: 0.03em;
+  word-break: keep-all;
+  overflow-wrap: break-word;
+  text-align: justify;
+}
+
+/* Specific heading spacing improvements for CJK characters */
+html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
+html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
+html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
+  font-weight: 700;
+  letter-spacing: 0.02em;
+  margin-top: 1.4em;
+  margin-bottom: 0.6em;
+}
+
+/* Smooth fade and scale transition for dropdown active states */
+.dropdown-menu {
+  opacity: 0;
+  transform: translateY(8px) scale(0.98);
+  display: block;
+  visibility: hidden;
+  transition: opacity 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.2s;
+}
+
+.dropdown-menu.show {
+  opacity: 1;
+  transform: translateY(0) scale(1);
+  visibility: visible;
+}
+
 /* ========================================
-   PDF EXPORT PROGRESS MODAL
+   FIND & REPLACE FLOATING PANEL DESIGN
    ======================================== */
 
-.pdf-progress-overlay {
+.find-replace-panel {
   position: fixed;
-  inset: 0;
-  z-index: 2600;
+  top: 100px;
+  right: 20px;
+  width: 340px;
+  background-color: var(--fr-bg);
+  border: 1px solid var(--fr-border);
+  border-radius: 12px;
+  box-shadow: var(--fr-shadow);
+  z-index: 1050;
+  display: flex;
+  flex-direction: column;
+  backdrop-filter: blur(10px);
+  -webkit-backdrop-filter: blur(10px);
+  transition: opacity 0.2s ease, transform 0.2s ease;
+  user-select: none;
+  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+}
+
+.find-replace-panel.docked {
+  position: relative;
+  top: 0 !important;
+  right: 0 !important;
+  height: 100%;
+  border-radius: 0;
+  border-top: none;
+  border-bottom: none;
+  border-right: none;
+  border-left: 1px solid var(--fr-border);
+  box-shadow: none;
+  backdrop-filter: none;
+  z-index: 10;
+  flex-shrink: 0;
+}
+
+.find-replace-panel.docked #find-replace-reset,
+.find-replace-panel.docked #find-replace-reset-footer {
+  display: none !important;
+}
+
+.find-replace-header {
   display: flex;
   align-items: center;
-  justify-content: center;
-  background: rgba(0, 0, 0, 0.45);
-  padding: 20px;
+  justify-content: space-between;
+  padding: 8px 12px;
+  border-bottom: 1px solid var(--fr-border);
+  cursor: move;
+  background-color: var(--header-bg);
+  border-top-left-radius: 11px;
+  border-top-right-radius: 11px;
 }
 
-.pdf-progress-modal {
-  width: min(92vw, 420px);
-  background: var(--header-bg);
-  border: 1px solid var(--border-color);
-  border-radius: 8px;
-  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.28);
+.find-replace-panel.docked .find-replace-header {
+  cursor: default;
+  border-top-left-radius: 0;
+  border-top-right-radius: 0;
+}
+
+.find-replace-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.find-replace-header-actions {
+  display: flex;
+  gap: 4px;
+}
+
+.panel-icon-btn {
+  background: none;
+  border: none;
   color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: background-color 0.15s ease;
+}
+
+.panel-icon-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.find-replace-body {
+  padding: 12px;
   display: flex;
   flex-direction: column;
-  gap: 16px;
-  padding: 20px;
+  gap: 8px;
 }
 
-.pdf-progress-header {
+.find-replace-field-row {
+  display: flex;
+  flex-direction: column;
+  position: relative;
+}
+
+.find-input-container, .replace-input-container {
   display: flex;
   align-items: center;
-  justify-content: space-between;
-  gap: 12px;
+  border: 1px solid var(--fr-border);
+  border-radius: 6px;
+  background-color: var(--bg-color);
+  padding: 2px 4px;
+  width: 100%;
 }
 
-.pdf-progress-title {
-  margin: 0;
-  font-size: 15px;
+.find-input-container:focus-within, .replace-input-container:focus-within {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 3px rgba(9, 105, 218, 0.15);
+}
+
+.find-input-field {
+  flex: 1;
+  border: none;
+  background: transparent;
+  color: var(--text-color);
+  font-size: 13px;
+  padding: 4px 6px;
+  outline: none;
+  width: 50%;
+}
+
+.find-options-group {
+  display: flex;
+  gap: 2px;
+}
+
+.find-option-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 11px;
   font-weight: 600;
+  cursor: pointer;
+  padding: 2px 5px;
+  border-radius: 4px;
+  transition: background-color 0.12s ease, color 0.12s ease;
+  min-width: 22px;
+  height: 22px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
 }
 
-.pdf-progress-percent {
-  font-size: 28px;
+.find-option-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+.find-option-btn.active {
+  background-color: var(--fr-btn-active-bg);
+  color: var(--fr-btn-active);
+}
+
+.find-error-drawer {
+  background-color: var(--fr-error-bg);
+  border: 1px solid var(--fr-error-border);
+  border-radius: 6px;
+  padding: 6px 10px;
+  font-size: 11px;
+  color: var(--fr-text-danger);
+  line-height: 1.3;
+}
+
+.find-replace-meta-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 2px 4px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary);
+}
+
+.find-nav-group {
+  display: flex;
+  gap: 4px;
+}
+
+.find-nav-arrow-btn {
+  background: none;
+  border: 1px solid var(--fr-border);
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 8px;
+  border-radius: 4px;
+  transition: background-color 0.15s ease;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.find-nav-arrow-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.find-nav-arrow-btn:disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+}
+
+.find-drawer-toggle-row {
+  border-top: 1px solid var(--fr-border);
+  margin-top: 4px;
+  padding-top: 6px;
+}
+
+.drawer-toggle-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 12px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  padding: 2px 4px;
+  border-radius: 4px;
+  transition: color 0.15s ease;
+}
+
+.drawer-toggle-btn:hover {
+  color: var(--text-color);
+}
+
+.find-replace-drawer-content {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 4px 6px;
+  border-top: 1px dashed var(--fr-border);
+  margin-top: 2px;
+  padding-top: 8px;
+}
+
+.drawer-field {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.drawer-field.check-field {
+  flex-direction: row;
+  align-items: center;
+  gap: 6px;
+  padding: 2px 0;
+}
+
+.drawer-label {
+  font-size: 11px;
   font-weight: 600;
-  line-height: 1;
+  color: var(--text-secondary);
 }
 
-.pdf-progress-track {
+.drawer-select {
   width: 100%;
-  height: 10px;
-  background: var(--button-bg);
-  border: 1px solid var(--border-color);
-  border-radius: 999px;
-  overflow: hidden;
+  padding: 4px 6px;
+  border-radius: 4px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  font-size: 12px;
+  outline: none;
 }
 
-.pdf-progress-fill {
-  width: 0%;
-  height: 100%;
-  background: var(--accent-color);
-  border-radius: inherit;
-  transition: width 0.18s ease;
+.drawer-checkbox {
+  margin: 0;
+  cursor: pointer;
 }
 
-.pdf-progress-details {
+.drawer-label-checkbox {
+  font-size: 12px;
+  color: var(--text-color);
+  cursor: pointer;
+}
+
+.find-replace-actions-footer {
   display: flex;
-  flex-direction: column;
   gap: 6px;
+  padding: 8px 12px 12px 12px;
+  border-top: 1px solid var(--fr-border);
+  background-color: var(--header-bg);
+  border-bottom-left-radius: 11px;
+  border-bottom-right-radius: 11px;
+}
+
+.find-replace-panel.docked .find-replace-actions-footer {
+  border-bottom-left-radius: 0;
+  border-bottom-right-radius: 0;
+}
+
+.fr-action-btn {
+  flex: 1;
+  padding: 6px 8px;
   font-size: 12px;
-  color: var(--text-secondary);
+  font-weight: 500;
+  border-radius: 6px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--button-bg);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease, border-color 0.15s ease;
+  text-align: center;
 }
 
-.pdf-progress-detail {
+.fr-action-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.fr-action-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.fr-action-btn.secondary {
+  max-width: 60px;
+}
+
+/* ========================================
+   DIFF PREVIEW CONTAINER
+   ======================================== */
+.diff-preview-body {
+  padding: 16px;
   display: flex;
-  justify-content: space-between;
+  flex-direction: column;
   gap: 12px;
 }
 
-.pdf-progress-detail strong {
-  color: var(--text-color);
-  font-weight: 600;
+.diff-container {
+  border: 1px solid var(--fr-border);
+  border-radius: 8px;
+  background-color: var(--bg-color);
+  max-height: 400px;
+  overflow: auto;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 12px;
+  line-height: 1.5;
 }
 
-.pdf-progress-actions {
+.diff-line {
   display: flex;
-  justify-content: flex-end;
+  padding: 1px 8px;
 }
 
-.tool-button.pdf-export-loading,
-.mobile-menu-item.pdf-export-loading {
+.diff-line.addition {
+  background-color: rgba(46, 160, 67, 0.15);
+  color: #3fb950;
+}
+
+.diff-line.deletion {
+  background-color: rgba(248, 81, 73, 0.15);
+  color: #f85149;
+}
+
+.diff-line.context {
+  color: var(--text-secondary);
+}
+
+.diff-line-num {
+  width: 40px;
+  flex-shrink: 0;
+  text-align: right;
+  padding-right: 12px;
+  border-right: 1px solid var(--fr-border);
+  user-select: none;
+  opacity: 0.5;
+}
+
+.diff-line-content {
+  padding-left: 12px;
+  white-space: pre-wrap;
+  word-break: break-all;
+}
+
+/* ========================================
+   DOCK LAYOUT CODES
+   ======================================== */
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-dock-wrapper {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-pane-inner {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  position: relative;
+  overflow: hidden;
+}
+
+/* ========================================
+   MOBILE & TABLET FIND PANEL RESPONSIVE FIXES
+   ======================================== */
+@media (max-width: 1079px) {
+  #find-replace-dock {
+    display: none !important;
+  }
+}
+
+@media (max-width: 768px) {
+  /* Prevent full screen expansion of floating panel on small mobile viewports */
+  .find-replace-panel {
+    width: calc(100% - 24px) !important;
+    right: 12px !important;
+    left: 12px !important;
+    top: 80px !important;
+  }
+}
+
+/* ========================================
+   SKELETON LOADING SHIMMER SYSTEM
+   ======================================== */
+.skeleton-placeholder {
+  display: block;
+  background-color: var(--skeleton-bg);
+  border-radius: 6px;
+  position: relative;
+  overflow: hidden;
+  /* PERF-017: Removed skeleton-pulse; shimmer-only is sufficient and halves GPU compositing layers */
+  /* animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate; */
+}
+
+.skeleton-placeholder::after {
+  content: "";
+  position: absolute;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  left: 0;
+  transform: translateX(-100%);
+  background-image: linear-gradient(
+    90deg,
+    rgba(255, 255, 255, 0) 0%,
+    var(--skeleton-glow) 50%,
+    rgba(255, 255, 255, 0) 100%
+  );
+  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
+}
+
+@keyframes skeleton-shimmer {
+  100% {
+    transform: translateX(100%);
+  }
+}
+
+@keyframes skeleton-pulse {
+  0%, 100% {
+    opacity: 1;
+  }
+  50% {
+    opacity: 0.82;
+  }
+}
+
+.skeleton-circle {
+  width: 32px;
+  height: 32px;
+  border-radius: 50%;
+  margin: 0 auto;
+}
+
+.skeleton-text {
+  height: 12px;
+  width: 80%;
+  margin: 4px auto;
+  border-radius: 3px;
+}
+
+.skeleton-tree-folder {
+  height: 16px;
+  width: 140px;
+  margin: 6px 0;
+  display: inline-block;
+}
+
+.skeleton-tree-file {
+  height: 14px;
+  width: 180px;
+  margin: 4px 0 4px 12px;
+  display: inline-block;
+}
+
+/* Screen reader accessibility utility */
+.visually-hidden {
+  position: absolute !important;
+  width: 1px !important;
+  height: 1px !important;
+  padding: 0 !important;
+  margin: -1px !important;
+  overflow: hidden !important;
+  clip: rect(0, 0, 0, 0) !important;
+  clip-path: inset(50%) !important;
+  white-space: nowrap !important;
+  border: 0 !important;
+}
+
+/* Article skeleton layout structures */
+.skeleton-title {
+  height: 28px;
+  width: 35%;
+  margin-bottom: 24px;
+  border-radius: 8px;
+}
+
+.skeleton-subtitle {
+  height: 20px;
+  width: 20%;
+  margin-bottom: 18px;
+  margin-top: 32px;
+  border-radius: 6px;
+}
+
+.skeleton-line {
+  height: 14px;
+  margin-bottom: 12px;
+  border-radius: 6px;
+}
+
+/* Symmetrical dynamic widths */
+.skeleton-w90 { width: 90%; }
+.skeleton-w92 { width: 92%; }
+.skeleton-w88 { width: 88%; }
+.skeleton-w85 { width: 85%; }
+.skeleton-w60 { width: 60%; }
+.skeleton-w45 { width: 45%; }
+
+/* Editor pane skeleton overlay */
+.editor-skeleton {
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  padding: 30px 24px 24px calc(24px + var(--line-number-gutter));
+  z-index: 10;
   pointer-events: none;
+  background: var(--editor-bg);
+  box-sizing: border-box;
+  overflow: hidden;
+  transition: opacity 0.3s ease;
+}
+
+.editor-pane:not(.is-loading) .editor-skeleton {
+  display: none;
+}
+
+.editor-pane.is-loading textarea {
+  opacity: 0; /* Completely hide editor content while initial bootstrap skeleton runs */
+}
+
+/* Preview pane skeleton container */
+.skeleton-preview-container {
+  display: block;
+  width: 100%;
+  box-sizing: border-box;
+  padding: 10px 4px;
+  background: transparent;
+  transition: opacity 0.3s ease;
+}
+
+/* Mermaid compilation loading states */
+.mermaid-container.is-loading {
+  min-height: 180px;
+  background-color: var(--skeleton-bg);
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  position: relative;
+  overflow: hidden;
+  animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate;
+}
+
+.mermaid-container.is-loading .mermaid {
+  opacity: 0; /* Hide raw chart source code during compile */
 }
-/* ========================================
-   RESET MODAL FORM FIELDS
-   ======================================== */
-
-.reset-modal-field {
-  display: flex;
-  flex-direction: column;
-  gap: 6px;
-  text-align: left;
-}
-
-.reset-modal-field-group {
-  display: flex;
-  flex-direction: column;
-  gap: 12px;
-}
-
-.reset-modal-label {
-  font-size: 12px;
-  color: var(--text-secondary, #57606a);
-  font-weight: 600;
-}
-
-.reset-modal-toggle-group {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-}
-
-.reset-modal-option {
-  display: flex;
-  align-items: center;
-  gap: 8px;
-  font-size: 13px;
-  color: var(--text-color);
-}
-
-.reset-modal-option input {
-  margin: 0;
-}
-
-/* ========================================
-   RENAME MODAL INPUT
-   ======================================== */
-
-.rename-modal-input {
-  width: 100%;
-  padding: 7px 10px;
-  border-radius: 6px;
-  border: 1px solid var(--border-color);
-  background: var(--bg-color);
-  color: var(--text-color);
-  font-size: 13px;
-  outline: none;
-  box-sizing: border-box;
-}
-
-.rename-modal-input:focus {
-  border-color: var(--accent-color);
-}
-
-/* ========================================
-   TOOLBAR POPUP PANELS
-   ======================================== */
-
-.reset-modal-box--xl {
-  width: min(94vw, 980px);
-  max-width: 980px;
-}
-
-.modal-empty {
-  margin: 0;
-  font-size: 12px;
-  color: var(--text-secondary, #57606a);
-  text-align: center;
-}
-
-.emoji-grid {
-  display: grid;
-  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
-  gap: 12px;
-  max-height: min(52vh, 440px);
-  overflow: auto;
-  padding: 4px;
-}
-
-.symbol-grid {
-  display: flex;
-  flex-direction: column;
-  gap: 16px;
-  max-height: min(52vh, 440px);
-  overflow: auto;
-  padding: 4px 2px;
-}
-
-.symbol-section-title {
-  margin: 0;
-  font-size: 11px;
-  text-transform: uppercase;
-  letter-spacing: 0.08em;
-  color: var(--text-secondary, #57606a);
-}
-
-.symbol-section-grid {
-  display: grid;
-  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
-  gap: 12px;
-}
-
-.alert-grid {
-  display: grid;
-  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
-  gap: 12px;
-  max-height: min(45vh, 360px);
-  overflow: auto;
-  padding: 2px;
-}
-
-.emoji-item,
-.symbol-item,
-.alert-option {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-  align-items: center;
-  border: 1px solid var(--border-color);
-  border-radius: 10px;
-  padding: 10px;
-  background: var(--bg-color);
-  color: var(--text-color);
-  cursor: pointer;
-  transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
-}
-
-.emoji-item:focus-visible,
-.symbol-item:focus-visible,
-.alert-option:focus-visible {
-  outline: 2px solid var(--accent-color);
-  outline-offset: 2px;
-}
-
-.emoji-item.is-selected,
-.symbol-item.is-selected,
-.alert-option.is-selected {
-  border-color: var(--accent-color);
-  box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
-  background-color: rgba(88, 166, 255, 0.08);
-}
-
-.emoji-preview {
-  width: 36px;
-  height: 36px;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-}
-
-.emoji-preview img {
-  width: 32px;
-  height: 32px;
-}
-
-.emoji-shortcode {
-  display: flex;
-  align-items: center;
-  gap: 6px;
-  font-size: 12px;
-  color: var(--text-secondary, #57606a);
-  text-align: center;
-}
-
-.emoji-copy-btn,
-.symbol-copy-btn {
-  border: none;
-  background: transparent;
-  color: var(--text-secondary, #57606a);
-  cursor: pointer;
-  padding: 2px;
-  border-radius: 4px;
-}
-
-.emoji-copy-btn:hover,
-.symbol-copy-btn:hover {
-  color: var(--text-color);
-  background: var(--button-hover);
-}
-
-.emoji-copy-btn.is-copied,
-.symbol-copy-btn.is-copied {
-  color: var(--accent-color);
-}
-
-.symbol-preview {
-  font-size: 28px;
-  line-height: 1;
-}
-
-.symbol-code {
-  display: flex;
-  align-items: center;
-  gap: 6px;
-  font-size: 12px;
-  color: var(--text-secondary, #57606a);
-}
-
-.alert-option {
-  align-items: stretch;
-  text-align: left;
-  padding: 12px;
-}
-
-.alert-preview {
-  margin: 0;
-}
-
-.alert-preview .markdown-alert {
-  padding: 0.5rem 0.9rem;
-  border-left: 0.25em solid;
-  border-radius: 0.375rem;
-}
-
-.alert-preview .markdown-alert-title {
-  margin: 0 0 6px;
-  font-weight: 600;
-  line-height: 1.25;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-}
-
-.alert-preview .markdown-alert-icon {
-  display: inline-flex;
-  width: 16px;
-  height: 16px;
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-  transition: background-color 0.15s ease, border-color 0.15s ease;
-  text-align: center;
-}
-
-.fr-action-btn:hover:not(:disabled) {
-  background-color: var(--button-hover);
-}
-
-.fr-action-btn:disabled {
-  opacity: 0.5;
-  cursor: not-allowed;
-}
-
-.fr-action-btn.secondary {
-  max-width: 60px;
-}
-
-/* ========================================
-   DIFF PREVIEW CONTAINER
-   ======================================== */
-.diff-preview-body {
-  padding: 16px;
-  display: flex;
-  flex-direction: column;
-  gap: 12px;
-}
-
-.diff-container {
-  border: 1px solid var(--fr-border);
-  border-radius: 8px;
-  background-color: var(--bg-color);
-  max-height: 400px;
-  overflow: auto;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 12px;
-  line-height: 1.5;
-}
-
-.diff-line {
-  display: flex;
-  padding: 1px 8px;
-}
-
-.diff-line.addition {
-  background-color: rgba(46, 160, 67, 0.15);
-  color: #3fb950;
-}
-
-.diff-line.deletion {
-  background-color: rgba(248, 81, 73, 0.15);
-  color: #f85149;
-}
-
-.diff-line.context {
-  color: var(--text-secondary);
-}
-
-.diff-line-num {
-  width: 40px;
-  flex-shrink: 0;
-  text-align: right;
-  padding-right: 12px;
-  border-right: 1px solid var(--fr-border);
-  user-select: none;
-  opacity: 0.5;
-}
-
-.diff-line-content {
-  padding-left: 12px;
-  white-space: pre-wrap;
-  word-break: break-all;
-}
-
-/* ========================================
-   DOCK LAYOUT CODES
-   ======================================== */
-.content-container {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-  position: relative;
-}
-
-.editor-dock-wrapper {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-  position: relative;
-}
-
-.editor-pane-inner {
-  display: flex;
-  flex-direction: column;
-  flex: 1;
-  position: relative;
-  overflow: hidden;
-}
-
-/* ========================================
-   MOBILE & TABLET FIND PANEL RESPONSIVE FIXES
-   ======================================== */
-@media (max-width: 1079px) {
-  #find-replace-dock {
-    display: none !important;
-  }
-}
-
-@media (max-width: 768px) {
-  /* Prevent full screen expansion of floating panel on small mobile viewports */
-  .find-replace-panel {
-    width: calc(100% - 24px) !important;
-    right: 12px !important;
-    left: 12px !important;
-    top: 80px !important;
-  }
-}
-
-/* ========================================
-   SKELETON LOADING SHIMMER SYSTEM
-   ======================================== */
-.skeleton-placeholder {
-  display: block;
-  background-color: var(--skeleton-bg);
-  border-radius: 6px;
-  position: relative;
-  overflow: hidden;
-  /* PERF-017: Removed skeleton-pulse; shimmer-only is sufficient and halves GPU compositing layers */
-  /* animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate; */
-}
-
-.skeleton-placeholder::after {
-  content: "";
-  position: absolute;
-  top: 0;
-  right: 0;
-  bottom: 0;
-  left: 0;
-  transform: translateX(-100%);
-  background-image: linear-gradient(
-    90deg,
-    rgba(255, 255, 255, 0) 0%,
-    var(--skeleton-glow) 50%,
-    rgba(255, 255, 255, 0) 100%
-  );
-  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
-}
-
-@keyframes skeleton-shimmer {
-  100% {
-    transform: translateX(100%);
-  }
-}
-
-@keyframes skeleton-pulse {
-  0%, 100% {
-    opacity: 1;
-  }
-  50% {
-    opacity: 0.82;
-  }
-}
-
-.skeleton-circle {
-  width: 32px;
-  height: 32px;
-  border-radius: 50%;
-  margin: 0 auto;
-}
-
-.skeleton-text {
-  height: 12px;
-  width: 80%;
-  margin: 4px auto;
-  border-radius: 3px;
-}
-
-.skeleton-tree-folder {
-  height: 16px;
-  width: 140px;
-  margin: 6px 0;
-  display: inline-block;
-}
-
-.skeleton-tree-file {
-  height: 14px;
-  width: 180px;
-  margin: 4px 0 4px 12px;
-  display: inline-block;
-}
-
-/* Screen reader accessibility utility */
-.visually-hidden {
-  position: absolute !important;
-  width: 1px !important;
-  height: 1px !important;
-  padding: 0 !important;
-  margin: -1px !important;
-  overflow: hidden !important;
-  clip: rect(0, 0, 0, 0) !important;
-  clip-path: inset(50%) !important;
-  white-space: nowrap !important;
-  border: 0 !important;
-}
-
-/* Article skeleton layout structures */
-.skeleton-title {
-  height: 28px;
-  width: 35%;
-  margin-bottom: 24px;
-  border-radius: 8px;
-}
-
-.skeleton-subtitle {
-  height: 20px;
-  width: 20%;
-  margin-bottom: 18px;
-  margin-top: 32px;
-  border-radius: 6px;
-}
-
-.skeleton-line {
-  height: 14px;
-  margin-bottom: 12px;
-  border-radius: 6px;
-}
-
-/* Symmetrical dynamic widths */
-.skeleton-w90 { width: 90%; }
-.skeleton-w92 { width: 92%; }
-.skeleton-w88 { width: 88%; }
-.skeleton-w85 { width: 85%; }
-.skeleton-w60 { width: 60%; }
-.skeleton-w45 { width: 45%; }
-
-/* Editor pane skeleton overlay */
-.editor-skeleton {
-  position: absolute;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  padding: 30px 24px 24px calc(24px + var(--line-number-gutter));
-  z-index: 10;
-  pointer-events: none;
-  background: var(--editor-bg);
-  box-sizing: border-box;
-  overflow: hidden;
-  transition: opacity 0.3s ease;
-}
-
-.editor-pane:not(.is-loading) .editor-skeleton {
-  display: none;
-}
-
-.editor-pane.is-loading textarea {
-  opacity: 0; /* Completely hide editor content while initial bootstrap skeleton runs */
-}
-
-/* Preview pane skeleton container */
-.skeleton-preview-container {
-  display: block;
-  width: 100%;
-  box-sizing: border-box;
-  padding: 10px 4px;
-  background: transparent;
-  transition: opacity 0.3s ease;
-}
-
-/* Mermaid compilation loading states */
-.mermaid-container.is-loading {
-  min-height: 180px;
-  background-color: var(--skeleton-bg);
-  border-radius: 8px;
-  border: 1px solid var(--border-color);
-  position: relative;
-  overflow: hidden;
-  animation: skeleton-pulse 2.2s cubic-bezier(0.4, 0, 0.2, 1) infinite alternate;
-}
-
-.mermaid-container.is-loading .mermaid {
-  opacity: 0; /* Hide raw chart source code during compile */
-}
-
-.mermaid-container.is-loading::after {
-  content: "";
-  position: absolute;
-  inset: 0;
-  transform: translateX(-100%);
-  background-image: linear-gradient(
-    90deg,
-    rgba(255, 255, 255, 0) 0%,
-    var(--skeleton-glow) 50%,
-    rgba(255, 255, 255, 0) 100%
-  );
-  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
-}
-
-/* Accessibility: respect user's motion preferences */
-@media (prefers-reduced-motion: reduce) {
-  .skeleton-placeholder,
-  .skeleton-placeholder::after,
-  .mermaid-container.is-loading,
-  .mermaid-container.is-loading::after {
-    animation: none;
-  }
-  .drag-overlay-inner {
-    animation: none;
-  }
-  .tab-item-new {
-    animation: none;
-  }
-  body,
-  .app-header,
-  .editor-pane,
-  .preview-pane,
-  .tool-button,
-  .markdown-tool-btn {
-    transition: none;
-  }
-}
-
\ No newline at end of file
+
+.mermaid-container.is-loading::after {
+  content: "";
+  position: absolute;
+  inset: 0;
+  transform: translateX(-100%);
+  background-image: linear-gradient(
+    90deg,
+    rgba(255, 255, 255, 0) 0%,
+    var(--skeleton-glow) 50%,
+    rgba(255, 255, 255, 0) 100%
+  );
+  animation: skeleton-shimmer 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
+}
+
+/* Accessibility: respect user's motion preferences */
+@media (prefers-reduced-motion: reduce) {
+  .skeleton-placeholder,
+  .skeleton-placeholder::after,
+  .mermaid-container.is-loading,
+  .mermaid-container.is-loading::after {
+    animation: none;
+  }
+  .drag-overlay-inner {
+    animation: none;
+  }
+  .tab-item-new {
+    animation: none;
+  }
+  body,
+  .app-header,
+  .editor-pane,
+  .preview-pane,
+  .tool-button,
+  .markdown-tool-btn {
+    transition: none;
+  }
+}
+
+/* ========================================
+   BROWSER PRINT STYLES
+   ======================================== */
+@media print {
+  body * {
+    visibility: hidden;
+  }
+  #markdown-preview, #markdown-preview * {
+    visibility: visible;
+  }
+  #markdown-preview {
+    position: absolute;
+    left: 0;
+    top: 0;
+    width: 100% !important;
+    height: auto !important;
+    margin: 0 !important;
+    padding: 0 !important;
+    overflow: visible !important;
+    box-shadow: none !important;
+    border: none !important;
+    background: transparent !important;
+  }
+  .preview-pane {
+    position: static !important;
+    width: 100% !important;
+    height: auto !important;
+    overflow: visible !important;
+    margin: 0 !important;
+    padding: 0 !important;
+    box-shadow: none !important;
+    border: none !important;
+    background: transparent !important;
+  }
+  .content-container {
+    display: block !important;
+    position: static !important;
+    width: 100% !important;
+    height: auto !important;
+    overflow: visible !important;
+  }
+  header, .tab-bar, .markdown-format-toolbar, .editor-pane, .resize-divider, #line-numbers, .pdf-progress-overlay {
+    display: none !important;
+  }
+}
\ No newline at end of file

From 769583236fce9adcda2055911e9d88c8ff17702e Mon Sep 17 00:00:00 2001
From: Baivab Sarkar <baivabsarkar@gmail.com>
Date: Thu, 11 Jun 2026 11:59:02 +0530
Subject: [PATCH 3/4] fix: add @page margin configuration to browser print
 stylesheet

---
 desktop-app/resources/styles.css | 3 +++
 styles.css                       | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/desktop-app/resources/styles.css b/desktop-app/resources/styles.css
index c0c8401f..00c3f70b 100644
--- a/desktop-app/resources/styles.css
+++ b/desktop-app/resources/styles.css
@@ -3875,6 +3875,9 @@ html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang=
    BROWSER PRINT STYLES
    ======================================== */
 @media print {
+  @page {
+    margin: 20mm 15mm !important;
+  }
   body * {
     visibility: hidden;
   }
diff --git a/styles.css b/styles.css
index c0c8401f..00c3f70b 100644
--- a/styles.css
+++ b/styles.css
@@ -3875,6 +3875,9 @@ html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang=
    BROWSER PRINT STYLES
    ======================================== */
 @media print {
+  @page {
+    margin: 20mm 15mm !important;
+  }
   body * {
     visibility: hidden;
   }

From 0f8192fd05cea906227dd0a91c48d848581571e8 Mon Sep 17 00:00:00 2001
From: Baivab Sarkar <baivabsarkar@gmail.com>
Date: Thu, 11 Jun 2026 12:04:32 +0530
Subject: [PATCH 4/4] style: add margins and format layout for browser print

---
 desktop-app/resources/styles.css | 49 ++++++++++++++------------------
 styles.css                       | 49 ++++++++++++++------------------
 2 files changed, 42 insertions(+), 56 deletions(-)

diff --git a/desktop-app/resources/styles.css b/desktop-app/resources/styles.css
index 00c3f70b..90facaaf 100644
--- a/desktop-app/resources/styles.css
+++ b/desktop-app/resources/styles.css
@@ -3876,46 +3876,39 @@ html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang=
    ======================================== */
 @media print {
   @page {
-    margin: 20mm 15mm !important;
+    margin: 15mm 15mm 15mm 15mm;
   }
-  body * {
-    visibility: hidden;
+  body {
+    background: #ffffff !important;
+    color: #000000 !important;
   }
-  #markdown-preview, #markdown-preview * {
-    visibility: visible;
+  /* Hide all UI layout components */
+  header, 
+  .tab-bar, 
+  .markdown-format-toolbar, 
+  .editor-pane, 
+  .resize-divider, 
+  .pdf-progress-overlay,
+  .reset-modal-overlay,
+  .drag-overlay,
+  #mobile-menu-overlay,
+  .mermaid-toolbar,
+  #line-numbers {
+    display: none !important;
   }
+  /* Ensure preview container fills the page with correct margins */
+  .content-container,
+  .preview-pane,
   #markdown-preview {
-    position: absolute;
-    left: 0;
-    top: 0;
+    display: block !important;
     width: 100% !important;
     height: auto !important;
     margin: 0 !important;
     padding: 0 !important;
     overflow: visible !important;
-    box-shadow: none !important;
-    border: none !important;
-    background: transparent !important;
-  }
-  .preview-pane {
     position: static !important;
-    width: 100% !important;
-    height: auto !important;
-    overflow: visible !important;
-    margin: 0 !important;
-    padding: 0 !important;
     box-shadow: none !important;
     border: none !important;
     background: transparent !important;
   }
-  .content-container {
-    display: block !important;
-    position: static !important;
-    width: 100% !important;
-    height: auto !important;
-    overflow: visible !important;
-  }
-  header, .tab-bar, .markdown-format-toolbar, .editor-pane, .resize-divider, #line-numbers, .pdf-progress-overlay {
-    display: none !important;
-  }
 }
\ No newline at end of file
diff --git a/styles.css b/styles.css
index 00c3f70b..90facaaf 100644
--- a/styles.css
+++ b/styles.css
@@ -3876,46 +3876,39 @@ html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang=
    ======================================== */
 @media print {
   @page {
-    margin: 20mm 15mm !important;
+    margin: 15mm 15mm 15mm 15mm;
   }
-  body * {
-    visibility: hidden;
+  body {
+    background: #ffffff !important;
+    color: #000000 !important;
   }
-  #markdown-preview, #markdown-preview * {
-    visibility: visible;
+  /* Hide all UI layout components */
+  header, 
+  .tab-bar, 
+  .markdown-format-toolbar, 
+  .editor-pane, 
+  .resize-divider, 
+  .pdf-progress-overlay,
+  .reset-modal-overlay,
+  .drag-overlay,
+  #mobile-menu-overlay,
+  .mermaid-toolbar,
+  #line-numbers {
+    display: none !important;
   }
+  /* Ensure preview container fills the page with correct margins */
+  .content-container,
+  .preview-pane,
   #markdown-preview {
-    position: absolute;
-    left: 0;
-    top: 0;
+    display: block !important;
     width: 100% !important;
     height: auto !important;
     margin: 0 !important;
     padding: 0 !important;
     overflow: visible !important;
-    box-shadow: none !important;
-    border: none !important;
-    background: transparent !important;
-  }
-  .preview-pane {
     position: static !important;
-    width: 100% !important;
-    height: auto !important;
-    overflow: visible !important;
-    margin: 0 !important;
-    padding: 0 !important;
     box-shadow: none !important;
     border: none !important;
     background: transparent !important;
   }
-  .content-container {
-    display: block !important;
-    position: static !important;
-    width: 100% !important;
-    height: auto !important;
-    overflow: visible !important;
-  }
-  header, .tab-bar, .markdown-format-toolbar, .editor-pane, .resize-divider, #line-numbers, .pdf-progress-overlay {
-    display: none !important;
-  }
 }
\ No newline at end of file