/* ==============================
   CSS Custom Properties (Themes)
   ============================== */
:root {
  --color-bg: #ffffff;
  --color-surface: #f8f9fa;
  --color-surface-2: #e9ecef;
  --color-border: #dee2e6;
  --color-text: #212529;
  --color-text-muted: #6c757d;
  --color-primary: #0d6efd;
  --color-primary-hover: #0b5ed7;
  --color-danger: #dc3545;
  --color-danger-hover: #b02a37;
  --color-header-bg: #1e1e2e;
  --color-header-text: #ffffff;
  --color-pane-header: #f1f3f4;
  --color-editor-bg: #ffffff;
  --color-preview-bg: #ffffff;
  --color-code-bg: #f6f8fa;
  --color-scrollbar: #c1c1c1;
  --color-toast-bg: #333;
  --color-toast-text: #fff;
  --color-toc-bg: #ffffff;
  --color-history-bg: #ffffff;
  --color-overlay: rgba(0, 0, 0, 0.5);
  --font-mono: 'Cascadia Code', 'Fira Code', 'Consolas', 'Monaco', monospace;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  --header-height: 52px;
  --transition: 0.2s ease;
  --border-radius: 6px;
  --shadow: 0 2px 8px rgba(0,0,0,0.1);
  --shadow-lg: 0 4px 20px rgba(0,0,0,0.15);
}

[data-theme="dark"] {
  --color-bg: #1a1a2e;
  --color-surface: #16213e;
  --color-surface-2: #0f3460;
  --color-border: #2d3748;
  --color-text: #e2e8f0;
  --color-text-muted: #a0aec0;
  --color-primary: #4299e1;
  --color-primary-hover: #3182ce;
  --color-danger: #fc8181;
  --color-danger-hover: #f56565;
  --color-header-bg: #0d0d1a;
  --color-header-text: #e2e8f0;
  --color-pane-header: #16213e;
  --color-editor-bg: #1a1a2e;
  --color-preview-bg: #1a1a2e;
  --color-code-bg: #0d1117;
  --color-scrollbar: #4a5568;
  --color-toast-bg: #e2e8f0;
  --color-toast-text: #1a202c;
  --color-toc-bg: #16213e;
  --color-history-bg: #16213e;
  --color-overlay: rgba(0, 0, 0, 0.7);
}

/* ==============================
   Theme transition
   ============================== */
body,
body *,
body *::before,
body *::after {
  transition:
    background-color 0.25s ease,
    color 0.25s ease,
    border-color 0.25s ease;
}

/* Exempt elements where transition would look jarring */
.btn,
.code-copy-btn,
.toast,
pre code,
.hljs-line-numbers {
  transition:
    background-color 0.15s ease,
    color 0.15s ease,
    border-color 0.15s ease,
    opacity 0.2s ease,
    transform 0.1s ease;
}

/* ==============================
   Reset & Base
   ============================== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  height: 100%;
  font-size: 16px;
}

body {
  height: 100%;
  display: flex;
  flex-direction: column;
  font-family: var(--font-sans);
  background-color: var(--color-bg);
  color: var(--color-text);
  transition: background-color var(--transition), color var(--transition);
  overflow: hidden;
}

/* ==============================
   Header
   ============================== */
.app-header {
  height: var(--header-height);
  background-color: var(--color-header-bg);
  color: var(--color-header-text);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  gap: 12px;
  flex-shrink: 0;
  z-index: 100;
  box-shadow: 0 2px 8px rgba(0,0,0,0.3);
}

.app-title {
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: -0.3px;
  color: var(--color-header-text);
  white-space: nowrap;
}

.header-controls {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: nowrap;
  overflow-x: auto;
}

/* ==============================
   Buttons
   ============================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 12px;
  font-size: 0.82rem;
  font-weight: 500;
  border: 1px solid transparent;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: background-color var(--transition), border-color var(--transition), transform 0.1s;
  white-space: nowrap;
  text-decoration: none;
  line-height: 1.4;
}

.btn:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

.btn:active {
  transform: scale(0.97);
}

.btn-primary {
  background-color: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.btn-primary:hover {
  background-color: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
}

.btn-secondary {
  background-color: rgba(255,255,255,0.1);
  color: var(--color-header-text);
  border-color: rgba(255,255,255,0.2);
}

.btn-secondary:hover {
  background-color: rgba(255,255,255,0.2);
}

.btn-danger {
  background-color: var(--color-danger);
  color: #fff;
  border-color: var(--color-danger);
}

.btn-danger:hover {
  background-color: var(--color-danger-hover);
}

.btn-icon {
  padding: 6px 8px;
  background: rgba(255,255,255,0.1);
  color: var(--color-header-text);
  border-color: rgba(255,255,255,0.2);
  font-size: 1rem;
}

.btn-icon:hover {
  background-color: rgba(255,255,255,0.2);
}

.btn-sm {
  padding: 4px 10px;
  font-size: 0.78rem;
}

/* Buttons inside panels (non-header) */
.history-actions .btn,
.toc-header .btn-icon {
  background-color: var(--color-surface-2);
  color: var(--color-text);
  border-color: var(--color-border);
}

.history-actions .btn-primary {
  background-color: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.history-actions .btn-danger {
  background-color: var(--color-danger);
  color: #fff;
}

.history-header .btn-icon,
.toc-header .btn-icon {
  background: none;
  border: none;
  color: var(--color-text-muted);
  font-size: 1.3rem;
  padding: 4px 8px;
}

.history-header .btn-icon:hover,
.toc-header .btn-icon:hover {
  color: var(--color-text);
  background-color: var(--color-surface-2);
}

/* ==============================
   Main Layout
   ============================== */
.app-main {
  flex: 1;
  display: flex;
  overflow: hidden;
  position: relative;
  height: calc(100vh - var(--header-height));
}

.pane {
  display: flex;
  flex-direction: column;
  overflow: hidden;
  min-width: 200px;
}

.pane-editor {
  flex: 1;
}

.pane-preview {
  flex: 1;
  border-left: 1px solid var(--color-border);
}

.pane-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 6px 14px;
  background-color: var(--color-pane-header);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.pane-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
}

.word-count {
  font-size: 0.72rem;
  color: var(--color-text-muted);
}

/* ==============================
   Editor
   ============================== */
.editor {
  flex: 1;
  width: 100%;
  padding: 20px;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  line-height: 1.7;
  background-color: var(--color-editor-bg);
  color: var(--color-text);
  border: none;
  resize: none;
  outline: none;
  transition: background-color var(--transition), color var(--transition);
  overflow-y: auto;
  tab-size: 2;
}

.editor::placeholder {
  color: var(--color-text-muted);
  opacity: 0.6;
}

/* ==============================
   Preview
   ============================== */
.preview {
  flex: 1;
  padding: 24px 28px;
  background-color: var(--color-preview-bg);
  color: var(--color-text);
  overflow-y: auto;
  line-height: 1.75;
  transition: background-color var(--transition), color var(--transition);
}

/* Preview Typography */
.preview h1, .preview h2, .preview h3,
.preview h4, .preview h5, .preview h6 {
  margin-top: 1.5em;
  margin-bottom: 0.5em;
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-text);
  scroll-margin-top: 20px;
}

.preview h1 { font-size: 2em; border-bottom: 2px solid var(--color-border); padding-bottom: 0.3em; }
.preview h2 { font-size: 1.5em; border-bottom: 1px solid var(--color-border); padding-bottom: 0.2em; }
.preview h3 { font-size: 1.25em; }
.preview h4 { font-size: 1em; }
.preview h5 { font-size: 0.875em; }
.preview h6 { font-size: 0.85em; color: var(--color-text-muted); }

.preview p { margin-bottom: 1em; }

.preview a {
  color: var(--color-primary);
  text-decoration: underline;
}

.preview a:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 2px;
}

.preview ul, .preview ol {
  margin-bottom: 1em;
  padding-left: 2em;
}

.preview li { margin-bottom: 0.25em; }

/* GFM task list checkboxes */
.preview li input[type="checkbox"] {
  margin-right: 0.4em;
  vertical-align: middle;
  cursor: default;
  accent-color: var(--color-primary);
}

.preview blockquote {
  border-left: 4px solid var(--color-primary);
  padding: 4px 16px;
  margin: 1em 0;
  color: var(--color-text-muted);
  background-color: var(--color-surface);
  border-radius: 0 var(--border-radius) var(--border-radius) 0;
}

.preview hr {
  border: none;
  border-top: 2px solid var(--color-border);
  margin: 2em 0;
}

.preview img {
  max-width: 100%;
  border-radius: var(--border-radius);
}

.preview table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1em;
  overflow-x: auto;
  display: block;
  font-size: 0.9em;
}

.preview th, .preview td {
  padding: 8px 14px;
  border: 1px solid var(--color-border);
  text-align: left;
}

.preview th {
  background-color: var(--color-surface);
  font-weight: 600;
}

.preview tr:nth-child(even) td {
  background-color: var(--color-surface);
}

/* ==============================
   Code Blocks
   ============================== */
.preview code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background-color: var(--color-code-bg);
  border-radius: 4px;
  padding: 2px 6px;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.preview pre {
  margin: 1em 0;
  border-radius: var(--border-radius);
  overflow: hidden;
  background-color: var(--color-code-bg);
  border: 1px solid var(--color-border);
  position: relative;
}

.preview pre code {
  display: block;
  padding: 16px 20px;
  overflow-x: auto;
  font-size: 0.875em;
  line-height: 1.6;
  background: none;
  border: none;
  border-radius: 0;
  color: inherit;
  flex: 1;
  min-width: 0;
}

/* Line numbers for syntax-highlighted blocks */
.preview pre.has-line-numbers {
  display: flex;
  align-items: flex-start;
  overflow: hidden;
}

.preview pre.has-line-numbers code {
  overflow-x: auto;
}

.hljs-line-numbers {
  display: block;
  padding: 16px 12px 16px 16px;
  font-family: var(--font-mono);
  font-size: 0.875em;
  line-height: 1.6;
  color: var(--color-text-muted);
  text-align: right;
  border-right: 1px solid var(--color-border);
  white-space: pre;
  user-select: none;
  flex-shrink: 0;
  opacity: 0.6;
}

.code-block-wrapper {
  position: relative;
}

.code-copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 10px;
  font-size: 0.72rem;
  font-weight: 500;
  background-color: rgba(255,255,255,0.15);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  cursor: pointer;
  opacity: 0;
  transition: opacity var(--transition), background-color var(--transition);
  z-index: 1;
}

.code-block-wrapper:hover .code-copy-btn,
.code-copy-btn:focus-visible {
  opacity: 1;
}

.code-copy-btn:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

.code-copy-btn:hover {
  background-color: rgba(255,255,255,0.25);
}

.code-copy-btn.copied {
  background-color: #198754;
  color: #fff;
  border-color: #198754;
}

.code-lang-badge {
  position: absolute;
  top: 8px;
  left: 12px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: lowercase;
  letter-spacing: 0.05em;
  pointer-events: none;
  user-select: none;
}

/* ==============================
   Pane Divider (resizable)
   ============================== */
.pane-divider {
  width: 5px;
  background-color: var(--color-border);
  cursor: col-resize;
  flex-shrink: 0;
  transition: background-color var(--transition);
  position: relative;
}

.pane-divider:hover,
.pane-divider:focus-visible,
.pane-divider.dragging {
  background-color: var(--color-primary);
}

.pane-divider:focus-visible {
  outline: none;
}

/* ==============================
   TOC Panel
   ============================== */
.toc-panel {
  position: fixed;
  top: var(--header-height);
  left: 0;
  bottom: 0;
  width: 280px;
  background-color: var(--color-toc-bg);
  border-right: 1px solid var(--color-border);
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  z-index: 200;
  transition: background-color var(--transition);
  overflow: hidden;
}

.toc-panel[hidden] {
  display: none;
}

.toc-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-pane-header);
  flex-shrink: 0;
}

.toc-title {
  font-size: 0.875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
}

#toc-nav {
  padding: 12px 0;
  overflow-y: auto;
  flex: 1;
}

.toc-empty {
  padding: 12px 16px;
  color: var(--color-text-muted);
  font-size: 0.875rem;
  font-style: italic;
}

.toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc-item {
  display: block;
}

.toc-link {
  display: block;
  padding: 5px 16px;
  font-size: 0.85rem;
  color: var(--color-text);
  text-decoration: none;
  transition: background-color var(--transition), color var(--transition);
  border-left: 3px solid transparent;
  line-height: 1.4;
}

.toc-link:hover {
  background-color: var(--color-surface);
  color: var(--color-primary);
  border-left-color: var(--color-primary);
}

.toc-link:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: -3px;
  border-radius: 2px;
}

.toc-link[data-level="2"] { padding-left: 28px; }
.toc-link[data-level="3"] { padding-left: 44px; font-size: 0.8rem; }
.toc-link[data-level="4"] { padding-left: 56px; font-size: 0.78rem; }
.toc-link[data-level="5"] { padding-left: 68px; font-size: 0.75rem; }
.toc-link[data-level="6"] { padding-left: 80px; font-size: 0.75rem; }

.toc-link-active {
  color: var(--color-primary);
  border-left-color: var(--color-primary);
  background-color: var(--color-surface);
  font-weight: 600;
}

.toc-insert-btn {
  display: block;
  margin: 8px 12px;
  width: calc(100% - 24px);
  background-color: var(--color-surface-2);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  text-align: center;
  font-size: 0.78rem;
}

.toc-insert-btn:hover {
  background-color: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

/* ==============================
   Version History Panel
   ============================== */
.history-panel {
  position: fixed;
  top: var(--header-height);
  right: 0;
  bottom: 0;
  width: 320px;
  background-color: var(--color-history-bg);
  border-left: 1px solid var(--color-border);
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  z-index: 200;
  transition: background-color var(--transition);
  overflow: hidden;
}

.history-panel[hidden] {
  display: none;
}

.history-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-pane-header);
  flex-shrink: 0;
}

.history-title {
  font-size: 0.875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
}

.history-actions {
  display: flex;
  gap: 8px;
  padding: 10px 16px;
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-surface);
  flex-shrink: 0;
}

.history-list {
  list-style: none;
  overflow-y: auto;
  flex: 1;
  padding: 8px 0;
}

.history-empty {
  padding: 16px;
  color: var(--color-text-muted);
  font-size: 0.875rem;
  font-style: italic;
  text-align: center;
}

.history-item {
  padding: 10px 16px;
  border-bottom: 1px solid var(--color-border);
  cursor: pointer;
  transition: background-color var(--transition);
}

.history-item:hover {
  background-color: var(--color-surface);
}

.history-item:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: -3px;
}

.history-item-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 8px;
}

.history-item-label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--color-text);
  word-break: break-all;
  flex: 1;
}

.history-item-time {
  font-size: 0.72rem;
  color: var(--color-text-muted);
  white-space: nowrap;
}

.history-item-preview {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  margin-top: 4px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  font-family: var(--font-mono);
}

.history-item-actions {
  display: flex;
  gap: 6px;
  margin-top: 8px;
}

.history-item-actions .btn {
  font-size: 0.72rem;
  padding: 3px 8px;
  background-color: var(--color-surface-2);
  color: var(--color-text);
  border-color: var(--color-border);
}

.history-item-actions .btn-danger {
  background-color: transparent;
  color: var(--color-danger);
  border-color: var(--color-danger);
}

.history-item-actions .btn:hover {
  opacity: 0.8;
}

/* ==============================
   Drop Overlay
   ============================== */
.drop-overlay {
  position: absolute;
  /* inset fallback for older browsers */
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  inset: 0;
  background-color: var(--color-overlay);
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  -webkit-box-pack: center;
  -ms-flex-pack: center;
  justify-content: center;
  z-index: 300;
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
}

.drop-overlay[hidden] {
  display: none;
}

.drop-overlay-content {
  text-align: center;
  color: #fff;
  pointer-events: none;
}

.drop-overlay-content span {
  font-size: 4rem;
  display: block;
  margin-bottom: 12px;
}

.drop-overlay-content p {
  font-size: 1.5rem;
  font-weight: 600;
}

/* Highlight the editor pane border during drag */
.drag-active .pane-editor {
  outline: 3px dashed var(--color-primary);
  outline-offset: -3px;
}

/* ==============================
   Toast
   ============================== */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background-color: var(--color-toast-bg);
  color: var(--color-toast-text);
  padding: 10px 20px;
  border-radius: 24px;
  font-size: 0.875rem;
  font-weight: 500;
  z-index: 500;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transition: opacity 0.3s, transform 0.3s;
  pointer-events: none;
  max-width: 90vw;
  text-align: center;
}

.toast[hidden] {
  display: none;
}

.toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* ==============================
   Scrollbars
   ============================== */
.editor::-webkit-scrollbar,
.preview::-webkit-scrollbar,
.history-list::-webkit-scrollbar,
#toc-nav::-webkit-scrollbar {
  width: 6px;
}

.editor::-webkit-scrollbar-track,
.preview::-webkit-scrollbar-track,
.history-list::-webkit-scrollbar-track,
#toc-nav::-webkit-scrollbar-track {
  background: transparent;
}

.editor::-webkit-scrollbar-thumb,
.preview::-webkit-scrollbar-thumb,
.history-list::-webkit-scrollbar-thumb,
#toc-nav::-webkit-scrollbar-thumb {
  background-color: var(--color-scrollbar);
  border-radius: 3px;
}

/* ==============================
   Mobile Tab Bar
   ============================== */
.mobile-tabs {
  display: none; /* hidden on desktop */
  background-color: var(--color-pane-header);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.mobile-tab {
  flex: 1;
  padding: 10px 0;
  font-size: 0.875rem;
  font-weight: 500;
  background: none;
  color: var(--color-text-muted);
  border: none;
  border-bottom: 3px solid transparent;
  cursor: pointer;
  transition: color var(--transition), border-color var(--transition);
}

.mobile-tab.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  font-weight: 600;
}

.mobile-tab:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: -3px;
}

/* ==============================
   Responsive Layout
   ============================== */

/* Tablet: 768px and below */
@media (max-width: 768px) {
  .app-header {
    padding: 0 10px;
    height: 48px;
    --header-height: 48px;
  }

  .app-title {
    font-size: 0.95rem;
  }

  .btn {
    padding: 5px 8px;
    font-size: 0.78rem;
  }

  /* Hide text labels on small screens, keep icons */
  .btn-secondary span + span,
  .btn span:last-child {
    display: none;
  }

  /* Show mobile tab bar */
  .mobile-tabs {
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
  }

  /* Single-pane layout: tabs switch visible pane */
  .app-main {
    flex-direction: column;
    position: relative;
  }

  .pane-editor,
  .pane-preview {
    flex: 1 1 100%;
    width: 100%;
    min-width: 0;
    min-height: 0;
    border: none;
  }

  /* Hidden pane on mobile */
  .pane-editor.mobile-hidden,
  .pane-preview.mobile-hidden {
    display: none;
  }

  /* Hide the resize divider on mobile */
  .pane-divider {
    display: none;
  }

  .toc-panel,
  .history-panel {
    width: 100%;
    left: 0;
    right: 0;
    top: 48px;
    bottom: 0;
  }

  .preview {
    padding: 16px;
  }
}

/* Mobile: 480px and below */
@media (max-width: 480px) {
  .app-title {
    display: none;
  }

  .header-controls {
    gap: 4px;
  }

  .pane-editor {
    flex: 0 0 45%;
  }

  .pane-preview {
    flex: 0 0 55%;
  }

  .editor {
    padding: 12px;
    font-size: 0.82rem;
  }

  .preview {
    padding: 12px;
    font-size: 0.9rem;
  }
}

/* Large screens: full split view */
@media (min-width: 1400px) {
  .preview {
    padding: 32px 40px;
  }
}

/* ==============================
   Share Modal
   ============================== */
.modal-overlay {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  inset: 0;
  background-color: var(--color-overlay);
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  -webkit-box-pack: center;
  -ms-flex-pack: center;
  justify-content: center;
  z-index: 400;
  padding: 16px;
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
}

.modal-overlay[hidden] {
  display: none;
}

.modal {
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 520px;
  overflow: hidden;
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-pane-header);
}

.modal-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
}

.modal-close {
  background: none;
  border: none;
  color: var(--color-text-muted);
  font-size: 1.4rem;
  padding: 4px 8px;
  cursor: pointer;
  border-radius: var(--border-radius);
}

.modal-close:hover {
  background-color: var(--color-surface-2);
  color: var(--color-text);
}

.modal-body {
  padding: 20px;
}

.modal-desc {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 14px;
  line-height: 1.5;
}

.share-url-row {
  display: flex;
  gap: 8px;
  align-items: center;
}

.share-url-input {
  flex: 1;
  padding: 8px 12px;
  font-size: 0.82rem;
  font-family: var(--font-mono);
  background-color: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  outline: none;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.share-url-input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(13, 110, 253, 0.15);
}

.share-size-warning {
  margin-top: 10px;
  font-size: 0.78rem;
  color: #f0a500;
  background-color: rgba(240, 165, 0, 0.1);
  border: 1px solid rgba(240, 165, 0, 0.3);
  padding: 6px 10px;
  border-radius: var(--border-radius);
}

.share-size-warning[hidden] {
  display: none;
}

@media (max-width: 480px) {
  .share-url-row {
    flex-direction: column;
    align-items: stretch;
  }
}

/* ==============================
   Print styles
   ============================== */
@media print {
  .app-header,
  .pane-editor,
  .pane-divider,
  .toc-panel,
  .history-panel,
  .toast {
    display: none !important;
  }

  .pane-preview {
    flex: 1;
    border: none;
  }

  .preview {
    padding: 0;
  }
}

/* ==============================
   Focus visible (accessibility)
   ============================== */
:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

/* Skip link for screen readers */
.skip-link {
  position: absolute;
  top: -100%;
  left: 0;
  background-color: var(--color-primary);
  color: #fff;
  padding: 8px 16px;
  font-size: 0.875rem;
  z-index: 9999;
  text-decoration: none;
  border-radius: 0 0 var(--border-radius) 0;
}

.skip-link:focus {
  top: 0;
}

/* Screen-reader only utility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* Keyboard focus indicator: show focus ring only for keyboard nav */
.js-focus-keyboard :focus:not(:focus-visible) {
  outline: none;
}

/* High contrast / forced colors support */
@media (forced-colors: active) {
  .btn,
  .code-copy-btn,
  .toc-link,
  .history-item {
    forced-color-adjust: auto;
  }
}