:root {
  color-scheme: light dark;
  --font-sans: "Iosevka Aile", "Cascadia Code", "Segoe UI", sans-serif;
  --font-mono: "Cascadia Code", "Fira Code", ui-monospace, SFMono-Regular, Menlo, Monaco, monospace;

  --font-size-body: 16px;
  --font-size-body-sm: 14px;
  --font-size-h4: 18px;
  --font-size-h3: 20px;
  --font-size-h2: 24px;
  --font-size-h1: 32px;

  --line-height-body: 32px;
  --line-height-sm: 24px;
  --line-height-h4: 32px;
  --line-height-h3: 32px;
  --line-height-h2: 40px;
  --line-height-h1: 48px;

  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 28px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;

  --radius: 14px;

  /* prose typography */
  --prose-font-body: "Iosevka Aile", "Cascadia Code", "Segoe UI", sans-serif;
  --prose-font-heading: "Iosevka Aile", "Cascadia Code", "Segoe UI", sans-serif;
  --prose-line-height: 2em;
  --prose-h-weight: 600;
  --prose-h-border: 1px solid var(--color-border-subtle);
  --prose-blockquote-border-width: 3px;
  --prose-paragraph-spacing: 0;
  --prose-font-size: 16px;
  --prose-h-color: var(--color-text-primary);
  --prose-h-accent: var(--color-primary);
  --prose-bg-accent: color-mix(in srgb, var(--color-primary) 6%, transparent);
}

html[data-theme="dark"] {
  --color-bg-base: #0f1115;
  --color-bg-raised: #151922;
  --color-bg-floating: #1b2130;
  --color-bg-overlay: #20283a;
  --color-text-primary: #e9edf5;
  --color-text-secondary: #a7b1c2;
  --color-text-tertiary: #b5bfce; /* was #8c96a8 — Lc ≈ 80 on bg-base for 14px/400w Chinese */
  --color-text-placeholder: #6f7a8f;
  --color-text-disabled: #586174;
  --color-text-on-primary: #0b0d12;
  --color-border-strong: rgba(255, 255, 255, 0.40); /* was 0.22 — WCAG 2.2 §1.4.11 needs 3:1 */
  --color-border-subtle: rgba(255, 255, 255, 0.08);
  --color-bg-code: #0b0d12;
  --color-primary: #53d3a6;
  --color-primary-hover: #6be0b6;
  --color-primary-active: #3bbd90;
  --color-primary-text: #0b0d12;
  --color-focus-ring: #7cc3ff;
  --shadow-elevated: 0 18px 40px rgba(0, 0, 0, 0.35);
  --bg-decor-1: rgba(83, 211, 166, 0.12);
  --bg-decor-2: rgba(124, 195, 255, 0.15);
  --color-error-bg: #3b1111;
  --color-error-border: #ef4444;
  --color-error-text: #fca5a5;
}

html[data-theme="light"] {
  --color-bg-base: #f7f8fb;
  --color-bg-raised: #ffffff;
  --color-bg-floating: #eef2f8;
  --color-bg-overlay: #e6ebf4;
  --color-text-primary: #0f172a;
  --color-text-secondary: #334155;
  --color-text-tertiary: #3f506a; /* was #475569 — darkened for Lc ≈ 83 on bg-base */
  --color-text-placeholder: #64748b;
  --color-text-disabled: #94a3b8;
  --color-text-on-primary: #0b0d12;
  --color-border-strong: rgba(15, 23, 42, 0.72); /* was 0.3 — WCAG 2.2 §1.4.11 needs 3:1 */
  --color-border-subtle: rgba(15, 23, 42, 0.12);
  --color-bg-code: #e6ebf4;
  --color-primary: #4cc99f;
  --color-primary-hover: #66d7b1;
  --color-primary-active: #34b085;
  --color-primary-text: #0b0d12;
  --color-focus-ring: #2563eb;
  --shadow-elevated: 0 14px 28px rgba(15, 23, 42, 0.18);
  --bg-decor-1: rgba(76, 201, 159, 0.18);
  --bg-decor-2: rgba(37, 99, 235, 0.15);
  --color-error-bg: #fef2f2;
  --color-error-border: #ef4444;
  --color-error-text: #991b1b;
}


* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  height: 100vh;
  overflow: hidden;
  background: radial-gradient(circle at top, var(--bg-decor-1), transparent 45%),
    radial-gradient(circle at 25% 20%, var(--bg-decor-2), transparent 35%),
    var(--color-bg-base);
  font-family: var(--font-sans);
  font-size: var(--font-size-body);
  line-height: var(--line-height-body);
  color: var(--color-text-primary);
  line-break: strict;
  font-feature-settings: "halt" 1;
  word-break: normal;
  overflow-wrap: break-word;
}

.app {
  --sidebar-width: 320px;
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  height: calc(100vh - 44px);
  transition: grid-template-columns 0.25s ease;
}

.app.sidebar-collapsed .sidebar-resizer {
  display: none;
}

.sidebar {
  background: linear-gradient(160deg, var(--color-bg-overlay), var(--color-bg-raised));
  border-right: 1px solid var(--color-border-subtle);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  position: relative;
}

.sidebar-header {
  display: flex;
  align-items: center;
  flex-shrink: 0;
  padding: var(--space-5) var(--space-3) 0 var(--space-5);
  gap: var(--space-3);
}

.app.sidebar-collapsed .sidebar-header {
  justify-content: center;
  padding-left: 0;
  padding-right: 0;
  gap: 0;
}

.sidebar-header-content {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: var(--space-2);
  flex: 1;
  min-width: 0;
  overflow: hidden;
  transition: opacity 0.15s ease;
}

.app.sidebar-collapsed .sidebar-header-content {
  flex: 0 0 0;
  width: 0;
  opacity: 0;
  pointer-events: none;
}

.sidebar-body {
  flex: 1;
  min-height: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
  padding: var(--space-4) var(--space-5) var(--space-4);
  overflow: hidden;
  transition: opacity 0.15s ease;
}

.app.sidebar-collapsed .sidebar-body {
  opacity: 0;
  pointer-events: none;
}

.sidebar h1 {
  margin: 0;
  font-size: var(--font-size-h3);
  line-height: var(--line-height-h3);
  font-weight: 600;
}

.sidebar-header .primary {
  box-shadow: none;
}

.sidebar-collapsed-label {
  display: none;
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  font-weight: 600;
  white-space: nowrap;
  letter-spacing: 0.05em;
  align-self: center;
  margin-top: var(--space-3);
  pointer-events: none;
}

.app.sidebar-collapsed .sidebar-collapsed-label {
  display: block;
}

.primary {
  background: var(--color-primary);
  color: var(--color-primary-text);
  border: none;
  border-radius: 999px;
  padding: var(--space-2) var(--space-4);
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  cursor: pointer;
  box-shadow: var(--shadow-elevated);
  min-height: 40px;
  white-space: nowrap;
  transition: background 0.15s ease, box-shadow 0.15s ease;
}

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

.primary .dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-primary-text);
  box-shadow: 0 0 0 4px rgba(11, 13, 18, 0.15);
}

.primary:focus-visible,
.ghost:focus-visible,
.theme-toggle-btn:focus-visible,
.tree button:focus-visible,
.tab:focus-visible,
.close-tab:focus-visible,
.paste-textarea:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.ghost {
  background: transparent;
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border-strong);
  border-radius: 999px;
  padding: var(--space-2) var(--space-4);
  font-weight: 600;
  min-height: 40px;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.ghost:hover {
  background: color-mix(in srgb, var(--color-text-secondary) 8%, transparent);
}

.tree {
  flex: 1;
  overflow: auto;
  padding-right: var(--space-2);
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.tree-entry {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.tree .node {
  display: grid;
  grid-template-columns: 16px minmax(0, 1fr);
  gap: var(--space-2);
  align-items: start;
  min-width: 0;
  padding: 6px var(--space-2);
  border-radius: 10px;
  color: var(--color-text-primary);
  background: transparent;
  border: 1px solid transparent;
  line-height: 1.5;
}

.tree .node:hover {
  background: color-mix(in srgb, var(--color-primary) 10%, transparent);
  border-color: color-mix(in srgb, var(--color-primary) 25%, transparent);
}

.tree .node[data-kind="directory"][data-expanded="true"] {
  background: color-mix(in srgb, var(--color-bg-floating) 76%, transparent);
  border-color: color-mix(in srgb, var(--color-border-strong) 26%, transparent);
}

.tree .node.active {
  background: color-mix(in srgb, var(--color-primary) 18%, transparent);
  border-color: color-mix(in srgb, var(--color-primary) 35%, transparent);
  color: var(--color-text-primary);
  box-shadow: inset 2px 0 0 var(--color-primary);
}

.tree .node .icon {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  line-height: 1;
  width: 16px;
  margin-top: 4px;
}

.tree .node .label {
  display: block;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.tree .node.active .label {
  white-space: normal;
  overflow: visible;
  text-overflow: clip;
  overflow-wrap: anywhere;
  word-break: break-word;
}

.tree .children {
  margin-left: 14px;
  border-left: 1px solid color-mix(in srgb, var(--color-border-strong) 22%, transparent);
  padding-left: var(--space-3);
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.tree .children[hidden] {
  display: none;
}

.sidebar-resizer {
  position: absolute;
  right: 0;
  top: 0;
  bottom: 0;
  width: 4px;
  cursor: col-resize;
  z-index: 10;
  transition: background 0.15s ease;
}

.sidebar-resizer:hover,
.sidebar-resizer.dragging {
  background: var(--color-primary);
}

.tree button {
  background: none;
  border: none;
  color: inherit;
  width: 100%;
  text-align: left;
  font: inherit;
  cursor: pointer;
  padding: 0;
}

.sidebar-footer {
  border-top: 1px solid var(--color-border-subtle);
  padding-top: var(--space-3);
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.footer-github-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  color: var(--color-text-tertiary);
  text-decoration: none;
  transition: color 0.15s ease;
  flex-shrink: 0;
}

.footer-bottom {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  flex-wrap: wrap;
}

.footer-separator {
  color: var(--color-text-disabled);
  font-weight: bold;
  user-select: none;
}

.footer-github-link:hover {
  color: var(--color-primary);
}

.footer-github-link svg {
  flex-shrink: 0;
}

.hint {
  margin: 0;
}

.copyright {
  margin: 0;
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  white-space: nowrap;
}

.workspace {
  display: flex;
  flex-direction: column;
  min-width: 0;
  min-height: 0;
  overflow: hidden;
}

.workspace.drag-over {
  position: relative;
}

.workspace.drag-over::after {
  content: attr(data-drag-hint);
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.35);
  border: 2px dashed var(--color-primary);
  color: #fff;
  font-size: var(--font-size-h4);
  font-weight: 600;
  letter-spacing: 0.02em;
  pointer-events: none;
  z-index: 100;
  border-radius: 4px;
  display: grid;
  place-items: center;
}

.topbar {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  border-bottom: 1px solid var(--color-border-subtle);
  flex-shrink: 0;
  padding: 0 var(--space-3);
}

.tabs {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) 0;
  flex-wrap: wrap;
  flex: 1;
  min-width: 0;
}

.search-box {
  display: flex;
  align-items: center;
}

.search-shell {
  position: relative;
  flex: 0 0 clamp(160px, 18vw, 220px);
  min-width: 160px;
  display: flex;
  align-items: center;
  min-height: 34px;
  margin: var(--space-2) 0;
}

.math-renderer-label {
  font-size: 12px;
  line-height: 1.4;
  font-weight: 600;
  color: var(--color-text-secondary);
}

.math-renderer-select {
  width: 100%;
  min-width: 180px;
  min-height: 34px;
  padding: 0 var(--space-3);
  border-radius: 12px;
  border: 1px solid var(--color-border-strong);
  background: color-mix(in srgb, var(--color-bg-raised) 90%, transparent);
  color: var(--color-text-primary);
  font: inherit;
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  cursor: pointer;
  transition: border-color 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}

.math-renderer-select:hover {
  border-color: color-mix(in srgb, var(--color-focus-ring) 35%, var(--color-border-strong));
}

.math-renderer-select:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
  border-color: color-mix(in srgb, var(--color-focus-ring) 45%, var(--color-border-strong));
}

.settings-dialog {
  width: min(560px, calc(100vw - 32px));
  max-width: 560px;
  padding: 0;
  border: none;
  background: transparent;
  color: inherit;
}

.settings-dialog::backdrop {
  background: rgba(15, 23, 42, 0.42);
  backdrop-filter: blur(6px);
}

.paste-dialog {
  width: min(760px, calc(100vw - 32px));
  max-width: 760px;
  padding: 0;
  border: none;
  background: transparent;
  color: inherit;
}

.paste-dialog::backdrop {
  background: rgba(15, 23, 42, 0.42);
  backdrop-filter: blur(6px);
}

.settings-panel {
  background: linear-gradient(180deg, color-mix(in srgb, var(--color-bg-raised) 92%, var(--color-bg-overlay)), var(--color-bg-raised));
  border: 1px solid var(--color-border-subtle);
  border-radius: calc(var(--radius) + 4px);
  box-shadow: var(--shadow-elevated);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.paste-panel {
  background: linear-gradient(180deg, color-mix(in srgb, var(--color-bg-raised) 94%, var(--color-bg-overlay)), var(--color-bg-raised));
  border: 1px solid var(--color-border-subtle);
  border-radius: calc(var(--radius) + 4px);
  box-shadow: var(--shadow-elevated);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.settings-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}

.paste-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
}

.settings-header-copy {
  min-width: 0;
}

.paste-header-copy {
  min-width: 0;
}

.settings-title {
  margin: 0;
  font-size: var(--font-size-h3);
  line-height: var(--line-height-h3);
}

.paste-title {
  margin: 0;
  font-size: var(--font-size-h3);
  line-height: var(--line-height-h3);
}

.settings-description {
  margin: var(--space-2) 0 0;
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
}

.paste-description {
  margin: var(--space-2) 0 0;
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
}

.paste-field {
  display: grid;
  gap: var(--space-2);
}

.paste-label {
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  font-weight: 600;
  color: var(--color-text-secondary);
}

.paste-textarea {
  width: 100%;
  min-height: min(44vh, 360px);
  resize: vertical;
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--color-bg-code) 68%, var(--color-bg-raised));
  color: var(--color-text-primary);
  padding: var(--space-4);
  font-family: var(--font-mono);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
}

.paste-textarea::placeholder {
  color: var(--color-text-placeholder);
}

.paste-actions {
  display: flex;
  justify-content: flex-end;
  gap: var(--space-2);
}

.settings-section {
  display: grid;
  gap: var(--space-4);
  padding: var(--space-4);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--color-bg-floating) 70%, transparent);
}

.settings-section-copy {
  min-width: 0;
}

.settings-section-title {
  margin: 0;
  font-size: var(--font-size-body);
  line-height: var(--line-height-body);
  font-weight: 600;
}

.settings-section-description {
  margin: var(--space-1) 0 0;
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
}

.math-renderer-field {
  display: grid;
  gap: var(--space-2);
  max-width: 240px;
}

/* ── Font controls ── */
.font-control {
  display: flex;
  gap: var(--space-2);
}

.font-control-btn {
  flex: 1;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius);
  background: var(--color-bg-raised);
  color: var(--color-text-secondary);
  font-family: var(--font-sans);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  cursor: pointer;
  transition: border-color 0.15s ease, background 0.15s ease, color 0.15s ease;
  text-align: center;
  user-select: none;
}

.font-control-btn:hover {
  border-color: var(--color-border-strong);
  color: var(--color-text-primary);
}

.font-control-btn.is-selected {
  border-color: var(--color-primary);
  background: color-mix(in srgb, var(--color-primary) 10%, var(--color-bg-raised));
  color: var(--color-text-primary);
}


.search-box input {
  width: 100%;
  min-height: 34px;
  border-radius: 999px;
  border: 1px solid var(--color-border-strong);
  background: color-mix(in srgb, var(--color-bg-raised) 90%, transparent);
  color: var(--color-text-primary);
  padding: 0 var(--space-3);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  transition: border-color 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}

.search-box input::placeholder {
  color: var(--color-text-placeholder);
}

.search-box input:hover {
  border-color: color-mix(in srgb, var(--color-focus-ring) 35%, var(--color-border-strong));
}

.search-box input:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
  border-color: color-mix(in srgb, var(--color-focus-ring) 45%, var(--color-border-strong));
}

.search-results {
  position: absolute;
  top: calc(100% + var(--space-2));
  left: 0;
  width: max(100%, 320px);
  max-width: min(520px, calc(100vw - var(--sidebar-width) - var(--space-6) * 2));
  max-height: min(50vh, 480px);
  overflow: auto;
  background: color-mix(in srgb, var(--color-bg-raised) 92%, var(--color-bg-overlay));
  border: 1px solid var(--color-border-subtle);
  border-radius: calc(var(--radius) + 2px);
  box-shadow: var(--shadow-elevated);
  padding: var(--space-4);
  backdrop-filter: blur(14px);
  z-index: 30;
}

.search-results[hidden] {
  display: none;
}

.search-result-group + .search-result-group {
  margin-top: var(--space-4);
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border-subtle);
}

.search-result-group-title {
  margin: 0 0 var(--space-2);
  color: var(--color-text-secondary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  font-weight: 700;
  letter-spacing: 0.02em;
}

.search-result-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.search-result-link {
  width: 100%;
  border: 1px solid transparent;
  border-radius: 12px;
  background: transparent;
  color: inherit;
  text-align: left;
  padding: var(--space-3);
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, transform 0.15s ease;
}

.search-result-link:hover {
  background: color-mix(in srgb, var(--color-primary) 10%, transparent);
  border-color: color-mix(in srgb, var(--color-primary) 22%, transparent);
  transform: translateY(-1px);
}

.search-result-link:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.search-result-path,
.search-result-meta,
.search-result-empty {
  display: block;
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
}

.search-result-title {
  display: block;
  color: var(--color-text-primary);
  font-weight: 600;
}

.search-result-path,
.search-result-meta {
  color: var(--color-text-tertiary);
}

.search-result-empty {
  color: var(--color-text-tertiary);
  padding: var(--space-1) 0;
}

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

.close-all-tabs-btn {
  flex-shrink: 0;
  margin-left: auto;
  margin-top: var(--space-2);
  margin-bottom: var(--space-2);
  display: flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-3);
  min-height: 32px;
  background: transparent;
  border: 1px solid var(--color-border-strong);
  border-radius: 999px;
  color: var(--color-text-secondary);
  font: inherit;
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.close-all-tabs-btn:hover {
  background: color-mix(in srgb, var(--color-text-secondary) 8%, transparent);
  color: var(--color-text-primary);
}

.close-all-tabs-btn:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.close-all-tabs-btn:active {
  background: color-mix(in srgb, var(--color-text-secondary) 14%, transparent);
}

.preview .katex {
  font-size: 1.05em;
}

.preview .katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  padding: var(--space-2) 0;
}

.preview mjx-container[jax="SVG"] {
  max-width: 100%;
}

.preview mjx-container[jax="SVG"][display="true"] {
  display: block;
  overflow-x: auto;
  overflow-y: hidden;
  padding: var(--space-2) 0;
}

.theme-toggle-btn {
  flex-shrink: 0;
  margin-top: var(--space-2);
  margin-bottom: var(--space-2);
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: none;
  border-radius: 8px;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
}

.theme-toggle-btn:hover {
  background: color-mix(in srgb, var(--color-text-secondary) 10%, transparent);
  color: var(--color-text-primary);
}

.tab {
  background: var(--color-bg-raised);
  border: 1px solid var(--color-border-subtle);
  border-radius: 999px;
  padding: 6px 12px;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-text-primary);
  cursor: pointer;
  min-height: 32px;
  font-size: var(--font-size-body-sm);
  line-height: 1.2;
  user-select: none;
  transition: background 0.15s ease, border-color 0.15s ease, opacity 0.15s ease, box-shadow 0.15s ease;
}

.tab:hover:not(.active) {
  background: color-mix(in srgb, var(--color-primary) 8%, var(--color-bg-raised));
  border-color: color-mix(in srgb, var(--color-primary) 20%, transparent);
}

.tab.active {
  background: var(--color-bg-floating);
  border-color: color-mix(in srgb, var(--color-focus-ring) 35%, transparent);
}

.tab[draggable="true"] {
  cursor: grab;
}

.tab.dragging {
  opacity: 0.55;
  cursor: grabbing;
}

.tab.drag-before {
  box-shadow: inset 3px 0 0 var(--color-focus-ring);
}

.tab.drag-after {
  box-shadow: inset -3px 0 0 var(--color-focus-ring);
}

.close-tab {
  border: none;
  background: transparent;
  color: var(--color-text-tertiary);
  font-size: 14px;
  cursor: pointer;
  min-height: 18px;
  min-width: 18px;
  padding: 0;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.viewer {
  flex: 1;
  padding: var(--space-6);
  overflow: auto;
}

.viewer-container {
  display: flex;
  align-items: flex-start;
  gap: var(--space-5);
}

.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: safe center;
  gap: var(--space-6);
  min-height: 100%;
  padding: var(--space-8) var(--space-6);
  box-sizing: border-box;
}

/* 有歷史紀錄時：左右並排 */
.empty-state.has-history {
  flex-direction: row;
  align-items: flex-start;
  justify-content: safe center;
  flex-wrap: wrap;
}

.empty-card {
  background: var(--color-bg-raised);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius);
  padding: var(--space-6);
  max-width: 420px;
  box-shadow: var(--shadow-elevated);
  flex-shrink: 0;
}

.empty-card h2 {
  margin-top: 0;
}

.empty-card ul {
  margin: var(--space-3) 0 0;
  padding-left: var(--space-4); /* was 18px — 非 4px 倍數，改為 16px */
  color: var(--color-text-tertiary);
}

.viewer-container {
  display: flex;
  align-items: flex-start;
  gap: var(--space-6);
  width: 100%;
  margin: 0;
  position: relative;
}

.viewer-container[hidden] {
  display: none;
}

.preview {
  display: block;
  flex: 1;
  min-width: 0;
  background: var(--color-bg-raised);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius);
  padding: var(--space-6) var(--space-7, 28px);
  line-height: var(--prose-line-height);
  font-family: var(--prose-font-body);
  font-size: var(--prose-font-size);
  box-shadow: var(--shadow-elevated);
}

.toc {
  width: 260px;
  flex-shrink: 0;
  position: sticky;
  top: 0;
  display: flex;
  flex-direction: column;
  max-height: calc(100vh - 44px - 44px - 2 * var(--space-6));
  background: var(--color-bg-raised);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius);
  box-shadow: var(--shadow-elevated);
  overflow: hidden;
  transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1),
              background 0.3s ease;
}

.toc.collapsed {
  width: 44px;
}

.toc-content {
  padding: var(--space-4);
  overflow-y: auto;
  opacity: 1;
  transition: opacity 0.2s ease 0.1s;
  flex: 1;
}

.toc.collapsed .toc-content {
  opacity: 0;
  pointer-events: none;
}

.toc-collapsed-label {
  display: none;
  writing-mode: vertical-rl;
  color: var(--color-text-tertiary);
  font-size: var(--font-size-body-sm);
  font-weight: 600;
  white-space: nowrap;
  letter-spacing: 0.05em;
  align-self: center;
  margin-top: var(--space-12);
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.2s ease;
}

.toc.collapsed .toc-collapsed-label {
  display: block;
  opacity: 1;
}
.toc-toggle-btn {
  position: absolute;
  top: var(--space-2);
  right: var(--space-2);
  width: 32px;
  height: 32px;
  border-radius: 8px;
  border: none;
  background: transparent;
  color: var(--color-text-secondary);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 20;
  transition: all 0.2s ease;
}

.toc-toggle-btn:hover {
  background: color-mix(in srgb, var(--color-text-secondary) 10%, transparent);
  color: var(--color-text-primary);
}

.toc.collapsed .toc-toggle-btn {
  top: 6px;
  right: 6px;
}

.toc-title {
  margin: 0 0 var(--space-3);
  padding-right: 40px;
  padding-bottom: var(--space-1);
  border-bottom: 1px solid var(--color-border-subtle);
  color: var(--color-text-primary);
  font-size: var(--font-size-h4);
  font-weight: 600;
}

#toc-list-container ul,
.toc-list {
  list-style: none;
  padding: 0;
  padding-left: 0;
  padding-inline-start: 0;
  margin: 0;
  margin-left: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

#toc-list-container li,
.toc-item {
  list-style: none;
  margin: 0;
}

.toc-item[data-level="1"] {
  list-style: none;
  margin: 0;
  padding-left: 0;
}

.toc-item[data-level="2"] {
  list-style: none;
  margin: 0;
  padding-left: var(--space-3);
}

.toc-item[data-level="3"] {
  list-style: none;
  margin: 0;
  padding-left: var(--space-5);
}

.toc-item[data-level="4"] {
  list-style: none;
  margin: 0;
  padding-left: var(--space-7);
}

.toc-link {
  display: block;
  padding: var(--space-1) var(--space-2);
  border-radius: 8px;
  color: var(--color-text-secondary);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  text-decoration: none;
  transition: background 0.15s ease, color 0.15s ease;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.toc-link:hover {
  background: color-mix(in srgb, var(--color-primary) 8%, transparent);
  color: var(--color-primary);
}

.toc-link.active {
  background: color-mix(in srgb, var(--color-primary) 12%, transparent);
  color: var(--color-primary);
  font-weight: 600;
}

.preview h1,
.preview h2,
.preview h3 {
  margin-top: var(--space-6);
  border-bottom: 1px solid var(--prose-h-accent);
  padding-bottom: var(--space-1);
  font-family: var(--prose-font-heading);
  font-weight: var(--prose-h-weight);
  color: var(--prose-h-color);
}

.preview h1 {
  font-size: var(--font-size-h1);
  line-height: var(--line-height-h1);
}

.preview h2 {
  font-size: var(--font-size-h2);
  line-height: var(--line-height-h2);
}

.preview h3 {
  font-size: var(--font-size-h3);
  line-height: var(--line-height-h3);
}

.preview h4 {
  color: var(--prose-h-color);
}

.preview pre {
  background: var(--color-bg-code);
  padding: var(--space-4);
  border-radius: 12px;
  overflow: auto;
  font-family: var(--font-mono);
}

.preview code {
  font-family: var(--font-mono);
}

.preview blockquote {
  border-left: var(--prose-blockquote-border-width) solid var(--prose-h-accent);
  margin-left: 0;
  padding-left: var(--space-3);
  color: var(--color-text-tertiary);
  background: var(--prose-bg-accent);
  padding-top: var(--space-2);
  padding-bottom: var(--space-2);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.preview p {
  margin-bottom: var(--prose-paragraph-spacing);
}

.preview table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-4) 0;
}

.preview th,
.preview td {
  border: 1px solid var(--color-border-subtle);
  padding: var(--space-2) var(--space-2);
}

.preview th {
  background: var(--prose-bg-accent);
}

.preview a {
  color: var(--prose-h-accent);
  text-decoration: underline;
}

.preview a:visited {
  color: color-mix(in srgb, var(--prose-h-accent) 70%, var(--color-text-tertiary));
}

.preview-image-missing {
  display: grid;
  place-items: center;
  width: 100%;
  min-height: 160px;
  margin: var(--space-4) 0;
  padding: var(--space-4);
  border: 1px dashed color-mix(in srgb, var(--color-border-strong) 70%, transparent);
  border-radius: 12px;
  background: color-mix(in srgb, var(--color-bg-code) 70%, transparent);
  color: var(--color-text-tertiary);
  text-align: center;
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
}

.preview .mermaid {
  background: var(--color-bg-code);
  padding: var(--space-3);
  border-radius: 12px;
  overflow: auto;
}

.statusbar {
  height: 44px;
  background: var(--color-bg-floating);
  border-top: 1px solid var(--color-border-subtle);
  display: flex;
  align-items: center;
  padding: 0 var(--space-5, 20px);
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  color: var(--color-text-tertiary);
}

.loading {
  position: relative;
  padding-left: 20px;
}

.loading::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 12px;
  height: 12px;
  border-radius: 50%;
  border: 2px solid color-mix(in srgb, var(--color-focus-ring) 35%, transparent);
  border-top-color: var(--color-focus-ring);
  animation: spin 0.9s linear infinite;
}

@keyframes spin {
  to {
    transform: translateY(-50%) rotate(360deg);
  }
}

@media (prefers-reduced-motion: reduce) {
  .loading::before {
    animation: none;
  }

  .app {
    transition: none;
  }
}

@media (max-width: 960px) {
  .app {
    grid-template-columns: 1fr;
  }

  .sidebar {
    border-right: none;
    border-bottom: 1px solid var(--color-border-subtle);
  }

  .topbar {
    flex-wrap: wrap;
    padding: var(--space-2);
  }

  .tabs {
    order: 1;
    width: 100%;
    padding: 0;
    gap: 6px;
  }

  .search-box {
    width: 100%;
  }

  .search-shell {
    order: 2;
    flex: 1 1 100%;
    min-width: 0;
  }

  .search-results {
    width: 100%;
    max-width: 100%;
  }

  .settings-panel {
    padding: var(--space-5);
  }

  .paste-panel {
    padding: var(--space-5);
  }

  .settings-header {
    gap: var(--space-3);
  }

  .paste-header {
    gap: var(--space-3);
  }

  .paste-actions {
    flex-direction: column-reverse;
  }

  .paste-actions .primary,
  .paste-actions .ghost {
    width: 100%;
    justify-content: center;
  }

  .math-renderer-field {
    max-width: none;
  }

  .viewer-container {
    display: block;
  }

  .toc {
    display: none;
  }
}

/* ── Toast notification ── */
.toast {
  position: fixed;
  top: var(--space-5);
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-error-bg);
  border: 1px solid var(--color-error-border);
  color: var(--color-error-text);
  border-radius: var(--radius);
  box-shadow: var(--shadow-elevated);
  padding: var(--space-3) var(--space-5);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  z-index: 9999;
  max-width: min(480px, calc(100vw - 40px));
  font-size: var(--font-size-body-sm);
  line-height: var(--line-height-sm);
  animation: toast-in 0.25s ease, toast-out 0.3s ease 4.7s forwards;
}

.toast-icon {
  flex-shrink: 0;
  font-size: 16px;
  line-height: 1;
}

.toast-message {
  flex: 1;
}

.toast-close {
  flex-shrink: 0;
  background: none;
  border: none;
  color: inherit;
  font-size: 18px;
  line-height: 1;
  cursor: pointer;
  padding: 0;
  opacity: 0.7;
  transition: opacity 0.15s ease;
}

.toast-close:hover {
  opacity: 1;
}

.toast-close:focus-visible {
  outline: 2px solid var(--color-error-border);
  outline-offset: 2px;
  border-radius: 2px;
}

@keyframes toast-in {
  from {
    opacity: 0;
    transform: translateX(-50%) translateY(-12px);
  }
  to {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
  }
}

@keyframes toast-out {
  from { opacity: 1; }
  to { opacity: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .toast {
    animation: none;
  }
}

/* ── Recent History ── */
.recent-history {
  background: var(--color-bg-raised);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius);
  padding: var(--space-6);
  box-shadow: var(--shadow-elevated);
  width: 100%;
  max-width: 420px;
  flex-shrink: 0;
}

/* 並排時改為彈性寬度，允許捲動 */
.has-history .recent-history {
  flex: 1 1 280px;
  max-width: 380px;
  max-height: calc(100vh - 8rem);
  overflow-y: auto;
  overscroll-behavior: contain;
}

.recent-title {
  margin: 0 0 var(--space-3);
  font-size: var(--font-size-body-sm);
  font-weight: 600;
  color: var(--color-text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.recent-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.recent-folder-item {
  background: var(--color-bg-raised);
  border: 1px solid var(--color-border-subtle);
  border-radius: 10px;
  overflow: hidden;
  transition: border-color 0.15s ease;
}

.recent-folder-item:hover {
  border-color: color-mix(in srgb, var(--color-primary) 35%, transparent);
}

.recent-folder-btn {
  display: block;
  width: 100%;
  text-align: left;
  background: transparent;
  border: none;
  font: inherit;
  font-size: var(--font-size-body-sm);
  font-weight: 600;
  color: var(--color-text-primary);
  padding: var(--space-2) var(--space-3);
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.recent-folder-btn:hover {
  background: color-mix(in srgb, var(--color-primary) 10%, transparent);
  color: var(--color-primary);
}

.recent-folder-btn:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: -2px;
}

.recent-folder-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.recent-files-list {
  list-style: none;
  padding: 0 0 var(--space-1);
  margin: 0;
  border-top: 1px solid var(--color-border-subtle);
  display: flex;
  flex-direction: column;
}

.recent-files-list li + li {
  border-top: 1px solid var(--color-border-subtle);
}

.recent-file-btn {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  width: 100%;
  text-align: left;
  background: transparent;
  border: none;
  font: inherit;
  font-size: var(--font-size-body-sm);
  color: var(--color-text-secondary);
  padding: var(--space-1) var(--space-3) var(--space-1) var(--space-6);
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
}

.recent-file-name {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

.recent-file-dir {
  font-size: calc(var(--font-size-body-sm) * 0.85);
  color: var(--color-text-muted, var(--color-text-secondary));
  opacity: 0.7;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

.recent-file-btn:hover {
  background: color-mix(in srgb, var(--color-primary) 8%, transparent);
  color: var(--color-primary);
}

.recent-file-btn:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: -2px;
}

.recent-file-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ── Sidebar Recent Panel ── */
.recent-panel {
  flex-shrink: 0;
}

.recent-panel-toggle {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  width: 100%;
  background: transparent;
  border: 1px solid transparent;
  border-radius: 10px;
  color: var(--color-text-secondary);
  font: inherit;
  font-size: var(--font-size-body-sm);
  font-weight: 600;
  padding: var(--space-1) var(--space-2);
  cursor: pointer;
  text-align: left;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.recent-panel-toggle:hover {
  background: color-mix(in srgb, var(--color-primary) 10%, transparent);
  border-color: color-mix(in srgb, var(--color-primary) 25%, transparent);
  color: var(--color-text-primary);
}

.recent-panel-toggle:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.recent-panel-icon {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 16px;
}

.recent-panel-label {
  flex: 1;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.recent-panel-chevron {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-left: auto;
}

.chevron-icon {
  transition: transform 0.2s ease;
}

.chevron-icon.rotated {
  transform: rotate(90deg);
}

.recent-panel-body {
  margin-top: var(--space-1);
  max-height: 240px;
  overflow-y: auto;
  overscroll-behavior: contain;
}

/* ── Prose themes ── */

html[data-prose-theme="vue"][data-theme="light"] {
  --prose-h-color: #2d7a4f;
  --prose-h-accent: #42b883;
  --prose-bg-accent: #f0fdf4;
}
html[data-prose-theme="vue"][data-theme="dark"] {
  --prose-h-color: #42b883;
  --prose-h-accent: #34d399;
  --prose-bg-accent: #052e16;
}

html[data-prose-theme="indigo"][data-theme="light"] {
  --prose-h-color: #4338ca;
  --prose-h-accent: #6366f1;
  --prose-bg-accent: #eef2ff;
}
html[data-prose-theme="indigo"][data-theme="dark"] {
  --prose-h-color: #818cf8;
  --prose-h-accent: #a5b4fc;
  --prose-bg-accent: #1e1b4b;
}

html[data-prose-theme="bear"][data-theme="light"] {
  --prose-h-color: #92400e;
  --prose-h-accent: #d97706;
  --prose-bg-accent: #fffbeb;
}
html[data-prose-theme="bear"][data-theme="dark"] {
  --prose-h-color: #f59e0b;
  --prose-h-accent: #fbbf24;
  --prose-bg-accent: #1c1008;
}