/**
 * MathEngine Mobile App Shell CSS
 * Fully responsive, edge-to-edge layout with safe-area insets, keyboard awareness,
 * multi-expression drawer, mode tabs, and export dialogs.
 */

:root {
  --keyboard-height: 0px;
  --safe-area-top: env(safe-area-inset-top, 0px);
  --safe-area-bottom: env(safe-area-inset-bottom, 0px);
  --safe-area-left: env(safe-area-inset-left, 0px);
  --safe-area-right: env(safe-area-inset-right, 0px);
  --app-usable-height: 100vh;

  /* Component-level Responsive Math Typography & Unified Input Metrics */
  --math-expr-font-size: clamp(1.0625rem, 0.96rem + 0.35vw, 1.25rem);
  --math-editor-font-size: clamp(1.125rem, 1.02rem + 0.4vw, 1.375rem);
  --math-result-font-size: 13.5px;
  --math-line-height: 1.25;
  --math-field-min-height: 32px;
  --math-field-pad-y: 4px;
  --math-field-pad-x: 8px;
  --math-content-pad-y: 2px;
  --math-content-pad-x: 2px;
  --fade-edge-rgb: 255, 255, 255;

  /* Default Theme: White / Light Theme */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-surface: #f1f5f9;
  --bg-card: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --accent-color: #2563eb;
  --accent-hover: #1d4ed8;
  --danger-color: #dc2626;
  --border-color: #e2e8f0;
  --border-strong: #cbd5e1;
}

[data-theme="light"] {
  --fade-edge-rgb: 255, 255, 255;
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-surface: #f1f5f9;
  --bg-card: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --accent-color: #2563eb;
  --accent-hover: #1d4ed8;
  --danger-color: #dc2626;
  --border-color: #e2e8f0;
  --border-strong: #cbd5e1;
}

[data-theme="dark"] {
  --fade-edge-rgb: 15, 23, 42;
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-surface: #334155;
  --bg-card: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --accent-color: #3b82f6;
  --accent-hover: #2563eb;
  --danger-color: #ef4444;
  --border-color: #475569;
  --border-strong: #64748b;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

html,
body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  position: fixed;
  inset: 0;
}

#app-container {
  display: flex;
  flex-direction: column;
  width: 100%;
  height: 100%;
  height: var(--app-usable-height, 100vh);
  padding-top: var(--safe-area-top);
  padding-left: var(--safe-area-left);
  padding-right: var(--safe-area-right);
  position: relative;
  overflow: hidden;
  container-type: inline-size;
  container-name: app-shell;
}

/* Header & Top Bar */
.app-header {
  position: relative;
  min-height: 52px;
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  justify-content: space-between;
  padding: 6px 12px;
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  z-index: 40;
  gap: 10px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 0 1 auto;
  min-width: 0;
}

.app-title {
  display: flex;
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 6px;
  white-space: nowrap;
  flex-shrink: 0;
}

.app-title img {
  width: 28px;
  height: 28px;
  object-fit: contain;
  display: block;
  flex-shrink: 0;
}

/* Mode Switcher Tabs */
.mode-tabs {
  display: flex;
  align-items: center;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 3px;
  gap: 2px;
  flex: 0 0 auto;
  min-width: 0;
}

.mode-tab-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  padding: 5px 12px;
  font-size: 13px;
  font-weight: 600;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
  white-space: nowrap;
  min-width: 0;
}

.mode-label-compact {
  display: none;
}

.mode-tab-btn:hover {
  color: var(--text-primary);
}

.mode-tab-btn.active {
  background-color: var(--accent-color);
  color: #ffffff;
}

.app-actions {
  display: flex;
  align-items: center;
  gap: 4px;
  flex: 0 0 auto;
}

.icon-btn.btn-more-actions {
  display: none;
}

/* Contextual Overflow Menu for Narrow Toolbar */
.header-overflow-menu {
  position: absolute;
  top: calc(100% + 6px);
  right: 8px;
  z-index: 60;
  min-width: 224px;
  max-width: calc(100vw - 16px);
  background: var(--bg-card);
  border: 1px solid var(--border-strong);
  border-radius: 12px;
  padding: 6px;
  display: flex;
  flex-direction: column;
  gap: 2px;
  box-shadow: 0 14px 34px rgba(15, 23, 42, 0.16), 0 4px 12px rgba(15, 23, 42, 0.08);
  opacity: 0;
  transform: translateY(-6px);
  pointer-events: none;
  visibility: hidden;
  transition: opacity 0.14s ease, transform 0.16s cubic-bezier(0.16, 1, 0.3, 1), visibility 0s linear 0.16s;
}

[data-theme="dark"] .header-overflow-menu {
  box-shadow: 0 16px 36px rgba(0, 0, 0, 0.5);
}

.header-overflow-menu.is-open {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
  visibility: visible;
  transition: opacity 0.14s ease, transform 0.16s cubic-bezier(0.16, 1, 0.3, 1), visibility 0s linear 0s;
}

.overflow-menu-item {
  width: 100%;
  min-height: 40px;
  padding: 8px 10px;
  border: none;
  border-radius: 8px;
  background: transparent;
  color: var(--text-primary);
  font-size: 13px;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 10px;
  text-align: left;
  cursor: pointer;
  transition: background-color 0.12s ease, color 0.12s ease;
}

.overflow-menu-item svg {
  color: var(--text-secondary);
  flex-shrink: 0;
}

.overflow-menu-item:hover,
.overflow-menu-item:focus-visible {
  background: var(--bg-surface);
  outline: none;
}

.icon-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 7px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.15s ease, color 0.15s ease;
}

.icon-btn:hover,
.icon-btn:active {
  background-color: var(--bg-surface);
  color: var(--text-primary);
}

.icon-btn.active {
  background-color: var(--accent-color);
  color: #ffffff;
}

/* Viewport Canvas (2D / 3D) */
#viewport-container {
  flex: 1 1 0;
  min-height: 0;
  position: relative;
  width: 100%;
  overflow: hidden;
  background-color: var(--bg-primary);
}

[data-theme="dark"] #viewport-container {
  background-color: #0b0f19;
}

#math-canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: block;
  touch-action: none;
}

/* Collapsible Expression & Tools Drawer */
#expression-drawer {
  position: absolute;
  top: 0;
  left: 0;
  width: clamp(360px, 28vw, 410px);
  max-width: 92vw;
  height: 100%;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-right: 1px solid var(--border-color);
  z-index: 30;
  display: flex;
  flex-direction: column;
  transition: transform 0.24s cubic-bezier(0.16, 1, 0.3, 1);
  box-shadow: 4px 0 24px rgba(0, 0, 0, 0.08);
}

[data-theme="dark"] #expression-drawer {
  background: rgba(15, 23, 42, 0.94);
  box-shadow: 4px 0 24px rgba(0, 0, 0, 0.35);
}

#expression-drawer.collapsed {
  transform: translateX(-100%);
  pointer-events: none;
}

.drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-color);
  background: rgba(248, 250, 252, 0.85);
  flex-shrink: 0;
}

[data-theme="dark"] .drawer-header {
  background: rgba(30, 41, 59, 0.5);
}

.drawer-title {
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.drawer-content {
  flex: 1 1 0;
  min-height: 80px;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 10px 12px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.slider-drawer-section {
  flex: 0 1 auto;
  max-height: 36%;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 8px 12px;
  border-top: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

/* Compact Collapsible Expression Creation Controls */
.drawer-footer {
  position: relative;
  padding: 8px 12px;
  border-top: 1px solid var(--border-color);
  background: rgba(248, 250, 252, 0.9);
  flex-shrink: 0;
}

[data-theme="dark"] .drawer-footer {
  background: rgba(30, 41, 59, 0.65);
}

.btn-add-expr-trigger {
  width: 100%;
  min-height: 38px;
  padding: 7px 12px;
  border-radius: 8px;
  border: 1px solid var(--border-strong);
  background: var(--bg-card);
  color: var(--text-primary);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.04);
  transition: border-color 0.15s ease, background-color 0.15s ease, color 0.15s ease;
}

.btn-add-expr-trigger:hover,
.btn-add-expr-trigger[aria-expanded="true"] {
  border-color: var(--accent-color);
  color: var(--accent-color);
}

.btn-add-expr-trigger[aria-expanded="true"] {
  background: rgba(37, 99, 235, 0.08);
}

[data-theme="dark"] .btn-add-expr-trigger[aria-expanded="true"] {
  background: rgba(59, 130, 246, 0.16);
}

.add-expr-trigger-label {
  display: inline-flex;
  align-items: center;
  gap: 7px;
}

.add-expr-trigger-chevron {
  transition: transform 0.18s ease;
}

.btn-add-expr-trigger[aria-expanded="true"] .add-expr-trigger-chevron {
  transform: rotate(180deg);
}

.add-expr-menu {
  position: absolute;
  left: 10px;
  right: 10px;
  bottom: calc(100% + 8px);
  z-index: 45;
  background: var(--bg-card);
  border: 1px solid var(--border-strong);
  border-radius: 12px;
  padding: 10px;
  box-shadow: 0 14px 34px rgba(15, 23, 42, 0.16), 0 4px 12px rgba(15, 23, 42, 0.08);
  max-height: min(360px, 54vh);
  overflow-y: auto;
  opacity: 0;
  transform: translateY(6px);
  pointer-events: none;
  visibility: hidden;
  transition: opacity 0.16s ease, transform 0.18s cubic-bezier(0.16, 1, 0.3, 1), visibility 0s linear 0.18s;
}

[data-theme="dark"] .add-expr-menu {
  box-shadow: 0 16px 36px rgba(0, 0, 0, 0.5);
}

.add-expr-menu.is-open {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
  visibility: visible;
  transition: opacity 0.16s ease, transform 0.18s cubic-bezier(0.16, 1, 0.3, 1), visibility 0s linear 0s;
}

.add-expr-menu-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 2px 8px;
  margin-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.add-expr-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 6px;
}

.btn-add {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--text-primary);
  padding: 7px 9px;
  font-size: 12.5px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
  gap: 2px;
  min-width: 0;
  text-align: left;
  transition: background-color 0.14s ease, border-color 0.14s ease, color 0.14s ease;
}

.btn-add-hint {
  font-size: 10.5px;
  font-weight: 500;
  color: var(--text-secondary);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

.btn-add:hover {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
  color: #ffffff;
}

.btn-add:hover .btn-add-hint {
  color: rgba(255, 255, 255, 0.85);
}

/* Expression Cards */
.expression-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-left: 3px solid var(--card-accent, var(--border-strong));
  border-radius: 9px;
  padding: 7px 10px 9px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
  max-width: 100%;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
  cursor: pointer;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}

[data-theme="dark"] .expression-card {
  box-shadow: none;
}

.expression-card:focus-within,
.expression-card.active-card {
  border-color: var(--accent-color);
  border-left-color: var(--card-accent, var(--accent-color));
  box-shadow: 0 0 0 1px var(--accent-color), 0 2px 10px rgba(37, 99, 235, 0.14);
}

[data-theme="dark"] .expression-card:focus-within,
[data-theme="dark"] .expression-card.active-card {
  box-shadow: 0 0 0 1px var(--accent-color), 0 2px 10px rgba(59, 130, 246, 0.2);
}

.expression-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 6px;
  width: 100%;
  min-height: 24px;
}

.expression-card-meta {
  display: flex;
  align-items: center;
  gap: 6px;
  min-width: 0;
}

.expression-card-actions {
  display: flex;
  align-items: center;
  gap: 2px;
  flex-shrink: 0;
}

.color-indicator {
  width: 13px;
  height: 13px;
  border-radius: 50%;
  cursor: pointer;
  flex-shrink: 0;
  border: 2px solid rgba(0, 0, 0, 0.16);
  transition: transform 0.12s ease;
}

.color-indicator:hover {
  transform: scale(1.12);
}

[data-theme="dark"] .color-indicator {
  border: 2px solid rgba(255, 255, 255, 0.6);
}

.visibility-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 3px;
  min-width: 24px;
  min-height: 24px;
  border-radius: 5px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.12s ease, color 0.12s ease;
}

.visibility-btn:hover {
  background-color: var(--bg-surface);
  color: var(--text-primary);
}

.visibility-btn.hidden {
  opacity: 0.42;
}

.expression-label {
  font-size: 10.5px;
  font-weight: 700;
  color: var(--text-secondary);
  min-width: 30px;
  text-align: center;
  padding: 2px 6px;
  border-radius: 5px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  flex-shrink: 0;
  line-height: 1.2;
}

.expression-domain-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 2px;
  padding-left: 0;
  font-size: 12px;
  color: var(--text-secondary);
}

.domain-select {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  color: var(--text-primary);
  font-size: 11px;
  padding: 2px 5px;
  cursor: pointer;
}

.domain-bound-input {
  width: 60px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  color: var(--text-primary);
  font-size: 12px;
  font-family: monospace;
  padding: 2px 6px;
  text-align: center;
}

.domain-range-label {
  font-family: 'Times New Roman', serif;
  font-style: italic;
  font-size: 13px;
}

.expression-error {
  margin-top: 6px;
  padding: 4px 8px;
  border-radius: 4px;
  background: rgba(239, 68, 68, 0.12);
  color: #dc2626;
  font-size: 11px;
  line-height: 1.35;
}

.expression-result {
  display: inline-flex;
  align-items: center;
  align-self: flex-end;
  gap: 4px;
  margin-top: 2px;
  padding: 4px 10px;
  border-radius: 6px;
  background: rgba(37, 99, 235, 0.08);
  border: 1px solid rgba(37, 99, 235, 0.22);
  color: var(--text-primary);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: var(--math-result-font-size);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  max-width: 100%;
  overflow-x: auto;
}

[data-theme="dark"] .expression-result {
  background: rgba(59, 130, 246, 0.16);
  border-color: rgba(96, 165, 250, 0.35);
}

.expression-matrix-result {
  flex-direction: column;
  align-items: flex-end;
  gap: 3px;
  padding: 6px 10px;
}

.matrix-meta {
  font-size: 10px;
  font-weight: 700;
  opacity: 0.72;
  letter-spacing: 0.03em;
}

.matrix-grid {
  display: grid;
  gap: 2px 10px;
  padding: 2px 6px;
  border-left: 2px solid currentColor;
  border-right: 2px solid currentColor;
  border-radius: 4px;
}

.matrix-cell {
  text-align: right;
  font-size: 12.5px;
  line-height: 1.35;
}

.expression-list-result {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 4px;
  max-width: 100%;
  word-break: break-word;
}

.expression-list-text {
  font-size: 12.5px;
  line-height: 1.35;
  text-align: right;
}

.btn-list-expand {
  font-size: 11px;
  font-weight: 600;
  color: var(--accent-color);
  background: transparent;
  border: none;
  padding: 0;
  cursor: pointer;
}

.expression-regression-result {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 2px;
  padding: 6px 10px;
  max-width: 100%;
}

.regression-eq {
  font-weight: 700;
  font-size: 13px;
}

.regression-params {
  font-size: 12px;
  opacity: 0.9;
}

.regression-stats {
  font-size: 11px;
  opacity: 0.72;
}

.family-members-row {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  margin-top: 6px;
}

.family-chip {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 7px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 11px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  cursor: pointer;
  transition: opacity 0.14s ease, border-color 0.14s ease;
}

.family-chip:hover {
  border-color: var(--accent-color);
}

.family-chip.is-hidden {
  opacity: 0.42;
  text-decoration: line-through;
}

.family-chip-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  display: inline-block;
  flex-shrink: 0;
}

.family-more-note {
  font-size: 11px;
  opacity: 0.68;
  padding: 2px 4px;
}

.geo-tool-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 5px;
}

#geometry-overlay {
  width: 300px;
  max-width: calc(100vw - 24px);
  box-sizing: border-box;
}

#geometry-overlay .overlay-row {
  min-width: 0;
}

.geo-tool-btn {
  padding: 5px 4px;
  font-size: 11.5px;
  font-weight: 600;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-primary);
  cursor: pointer;
  text-align: center;
  transition: all 0.12s ease;
}

.geo-tool-btn:hover {
  border-color: var(--accent-color);
}

.geo-tool-btn.active {
  background: var(--accent-color);
  color: #ffffff;
  border-color: var(--accent-color);
}

.geo-section-box {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding-top: 8px;
  border-top: 1px solid var(--border-color);
}

.geo-section-title {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-secondary);
}

.geo-inspector-fields {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 6px;
}

.geo-field-label {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 11.5px;
  color: var(--text-secondary);
  min-width: 0;
}

.geo-field-input {
  flex: 1;
  min-width: 0;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 5px;
  color: var(--text-primary);
  padding: 3px 6px;
  font-size: 12px;
}

.geo-danger-btn {
  padding: 3px 8px;
  font-size: 11px;
  font-weight: 600;
  border-radius: 5px;
  border: 1px solid rgba(220, 38, 38, 0.35);
  background: rgba(220, 38, 38, 0.08);
  color: #dc2626;
  cursor: pointer;
}

.geo-danger-btn:hover {
  background: rgba(220, 38, 38, 0.16);
}

.calc-readout {
  margin-top: 4px;
  padding: 6px 8px;
  border-radius: 6px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 11.5px;
  font-weight: 600;
  color: var(--text-primary);
  word-break: break-word;
}

.calc-checkbox-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  font-size: 11.5px;
  color: var(--text-secondary);
}

.calc-checkbox-row label {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  cursor: pointer;
}

.calc-table-wrap {
  max-height: 170px;
  overflow-y: auto;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  background: var(--bg-primary);
}

.calc-table {
  width: 100%;
  border-collapse: collapse;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 11px;
}

.calc-table th,
.calc-table td {
  padding: 4px 6px;
  border-bottom: 1px solid var(--border-color);
  text-align: right;
  font-variant-numeric: tabular-nums;
}

.calc-table th {
  text-align: right;
  font-weight: 700;
  color: var(--text-secondary);
  position: sticky;
  top: 0;
  background: var(--bg-primary);
}

.overlay-mini-btn {
  padding: 3px 8px;
  font-size: 11px;
  border-radius: 5px;
  border: 1px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-primary);
  cursor: pointer;
}

.overlay-mini-btn:hover {
  border-color: var(--accent-color);
}

.worksheet-status-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  min-width: 0;
  max-width: 210px;
  flex: 0 1 auto;
}

.worksheet-status-btn:hover {
  border-color: var(--accent-color);
}

#worksheet-title-display {
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.save-badge {
  font-size: 10px;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: 999px;
  flex-shrink: 0;
}

.save-badge.saved {
  background: rgba(16, 185, 129, 0.14);
  color: #059669;
}

.save-badge.saving {
  background: rgba(59, 130, 246, 0.15);
  color: #2563eb;
}

.save-badge.dirty {
  background: rgba(245, 158, 11, 0.16);
  color: #d97706;
}

.duplicate-btn,
.delete-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 4px;
  min-width: 26px;
  min-height: 26px;
  border-radius: 5px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
  transition: background-color 0.14s ease, color 0.14s ease;
}

.duplicate-btn:hover {
  background-color: var(--bg-surface);
  color: var(--accent-color);
}

.delete-btn:hover {
  background-color: rgba(220, 38, 38, 0.1);
  color: var(--danger-color);
}

.empty-worksheet-card {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 14px 12px;
  border: 1px dashed var(--border-color);
  border-radius: 10px;
  background: var(--bg-primary);
  text-align: center;
  font-size: 12px;
  color: var(--text-secondary);
}

.empty-quick-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 6px;
}

.ws-list-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 8px 10px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background: var(--bg-primary);
}

.ws-list-item.active-ws {
  border-color: var(--accent-color);
}

.ws-list-meta {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.ws-list-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-primary);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.ws-list-date {
  font-size: 10.5px;
  color: var(--text-secondary);
}

.ws-list-actions {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-shrink: 0;
}

.ws-danger-btn {
  color: #dc2626;
  border-color: rgba(239, 68, 68, 0.35);
}

.calc-table-x-input {
  width: 50px;
  padding: 2px 4px;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  background: var(--bg-secondary, var(--bg-primary));
  color: var(--text-primary);
  font-family: inherit;
  font-size: 11px;
  text-align: right;
}

.expression-card.has-error {
  border-color: rgba(239, 68, 68, 0.55);
}

/* Shared Scrollable Math Typography Container */
.math-scroll-shell {
  position: relative;
  display: flex;
  align-items: center;
  width: 100%;
  min-width: 0;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  overflow: hidden;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.math-scroll-shell:focus-within {
  border-color: var(--accent-color);
  box-shadow: 0 0 0 1px var(--accent-color);
}

.math-scroll-shell::before,
.math-scroll-shell::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  width: 22px;
  pointer-events: none;
  opacity: 0;
  z-index: 2;
  transition: opacity 0.15s ease;
}

.math-scroll-shell::before {
  left: 0;
  background: linear-gradient(to right, rgba(var(--fade-edge-rgb), 0.96) 20%, rgba(var(--fade-edge-rgb), 0));
}

.math-scroll-shell::after {
  right: 0;
  background: linear-gradient(to left, rgba(var(--fade-edge-rgb), 0.96) 20%, rgba(var(--fade-edge-rgb), 0));
}

.math-scroll-shell.can-scroll-left::before {
  opacity: 1;
}

.math-scroll-shell.can-scroll-right::after {
  opacity: 1;
}

.math-scroll-viewport {
  flex: 1 1 auto;
  min-width: 0;
  width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  -webkit-overflow-scrolling: touch;
  touch-action: pan-x pan-y;
  scrollbar-width: thin;
  scrollbar-color: var(--border-strong) transparent;
}

.math-scroll-viewport::-webkit-scrollbar {
  height: 5px;
}

.math-scroll-viewport::-webkit-scrollbar-track {
  background: transparent;
}

.math-scroll-viewport::-webkit-scrollbar-thumb {
  background: var(--border-strong);
  border-radius: 999px;
}

.math-scroll-viewport::-webkit-scrollbar-thumb:hover {
  background: var(--text-secondary);
}

/* Unified Math Field inside Scrollable Container (Sidebar Cards & Bottom Formula Bar) */
.math-scroll-field,
.expression-input,
.formula-input {
  flex: 1;
  min-width: 0;
  background: transparent;
  border: none;
  padding: var(--math-field-pad-y) var(--math-field-pad-x);
  color: var(--text-primary);
  font-size: var(--math-expr-font-size);
  line-height: var(--math-line-height);
  outline: none;
}

math-field.math-scroll-field,
math-field.expression-input,
math-field.formula-input {
  /* Block-level flex avoids inline-block + shadow inline wrapper creating extra line boxes */
  display: flex;
  align-items: center;
  box-sizing: border-box;
  min-width: 100%;
  width: max-content;
  min-height: var(--math-field-min-height);
  padding: var(--math-field-pad-y) var(--math-field-pad-x);
  color: var(--text-primary);
  font-size: var(--math-expr-font-size);
  line-height: var(--math-line-height);
  caret-color: var(--accent-color);
  --caret-color: var(--accent-color);
  --selection-background-color: rgba(59, 130, 246, 0.35);
  --contains-highlight-background-color: rgba(59, 130, 246, 0.2);
  cursor: text;
  border: none;
  background: transparent;
  outline: none;
  box-shadow: none;
}

math-field.math-scroll-field::part(container),
math-field.expression-input::part(container),
math-field.formula-input::part(container) {
  width: 100%;
  min-height: 0;
  display: flex;
  align-items: center;
  padding: 0;
  touch-action: pan-x pan-y;
}

math-field.math-scroll-field::part(content),
math-field.expression-input::part(content),
math-field.formula-input::part(content) {
  padding: var(--math-content-pad-y) var(--math-content-pad-x);
  line-height: var(--math-line-height);
  overflow: visible;
}

.math-scroll-field:focus,
.expression-input:focus,
.formula-input:focus,
math-field.math-scroll-field:focus-within,
math-field.expression-input:focus-within,
math-field.formula-input:focus-within {
  outline: none;
  box-shadow: none;
}

/* Mode-Specific Overlay Control Panels (Calculus & 3D) */
.mode-overlay {
  position: absolute;
  top: 14px;
  right: 14px;
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 12px 14px;
  z-index: 25;
  width: 290px;
  max-width: calc(100vw - 28px);
  display: flex;
  flex-direction: column;
  gap: 10px;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
  transition: all 0.22s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] .mode-overlay {
  background: rgba(30, 41, 59, 0.92);
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.4);
}

.mode-overlay.collapsed {
  width: auto;
  min-width: 0;
  padding: 7px 12px;
  gap: 0;
  border-radius: 20px;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.12);
}

.mode-overlay.collapsed .overlay-body {
  display: none;
}

.overlay-title {
  font-size: 13px;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  cursor: pointer;
  user-select: none;
}

.overlay-title-left {
  display: flex;
  align-items: center;
  gap: 6px;
}

.overlay-badge {
  font-size: 11px;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: 4px;
  background: var(--bg-surface);
  color: var(--accent-color);
  border: 1px solid var(--border-color);
}

.overlay-collapse-btn {
  background: transparent;
  border: none;
  cursor: pointer;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 4px;
  border-radius: 4px;
  transition: color 0.15s ease, background-color 0.15s ease;
}

.overlay-collapse-btn:hover {
  background-color: var(--bg-surface);
  color: var(--text-primary);
}

.chevron-icon {
  transition: transform 0.25s ease;
  transform: rotate(0deg);
}

.mode-overlay.collapsed .chevron-icon {
  transform: rotate(180deg);
}

.overlay-body {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

/* Floating Canvas Recenter / Navigation Control */
.floating-canvas-btn {
  position: absolute;
  bottom: 20px;
  right: 18px;
  z-index: 20;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--bg-card);
  border: 1px solid var(--border-strong);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.15);
  transition: transform 0.15s ease, box-shadow 0.15s ease, background-color 0.15s ease;
}

[data-theme="dark"] .floating-canvas-btn {
  background: #1e293b;
  border-color: #475569;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.4);
}

.floating-canvas-btn:hover {
  transform: scale(1.06);
  background-color: var(--bg-surface);
  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.2);
}

.floating-canvas-btn:active {
  transform: scale(0.94);
}

.overlay-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  font-size: 13px;
  color: var(--text-secondary);
}

.overlay-select,
.overlay-input {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-primary);
  padding: 5px 8px;
  font-size: 13px;
  outline: none;
}

.overlay-select {
  flex: 1;
  min-width: 0;
  max-width: 100%;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Dynamic Sliders UI (DOMSliderRenderer styles) */
.math-slider-card {
  background: rgba(248, 250, 252, 0.95);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 10px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.04);
}

[data-theme="dark"] .math-slider-card {
  background: rgba(30, 41, 59, 0.85);
  box-shadow: none;
}

.math-slider-header {
  display: flex;
  align-items: center;
  gap: 8px;
}

.math-slider-play-btn,
.math-slider-mode-btn {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-primary);
  cursor: pointer;
  padding: 4px 8px;
  font-size: 12px;
}

.math-slider-label {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-primary);
}

.math-slider-value {
  font-size: 13px;
  font-family: monospace;
  color: var(--accent-color);
  flex: 1;
  min-width: 56px;
  background: transparent;
  border: 1px solid transparent;
  border-radius: 4px;
  padding: 2px 4px;
}

.math-slider-value:focus {
  outline: none;
  background: var(--bg-primary);
  border-color: var(--border-color);
}

.math-slider-track-row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.math-slider-bound {
  width: 50px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  color: var(--text-primary);
  font-size: 12px;
  padding: 4px;
  text-align: center;
}

.math-slider-range {
  flex: 1;
  accent-color: var(--accent-color);
  cursor: pointer;
}

/* Bottom Math Formula Bar */
#math-input-bar {
  display: flex;
  align-items: center;
  padding: 5px 8px;
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  margin-bottom: var(--safe-area-bottom);
  z-index: 20;
  gap: 8px;
  transition: border-color 0.15s ease-out;
  cursor: text;
  flex-shrink: 0;
}

#app-container.has-math-keyboard #math-input-bar {
  margin-bottom: 0;
}

#math-input-bar:focus-within {
  border-top-color: var(--accent-color);
}

.formula-math-shell {
  flex: 1 1 0;
  min-width: 0;
  --math-field-min-height: 36px;
}

.formula-input,
math-field.formula-input {
  font-size: var(--math-editor-font-size);
}

.keyboard-toggle-btn {
  min-width: 38px;
  min-height: 38px;
  padding: 6px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-card);
  color: var(--text-secondary);
  flex-shrink: 0;
}

.keyboard-toggle-btn:hover {
  border-color: var(--accent-color);
  color: var(--accent-color);
}

.keyboard-toggle-btn.active {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
  color: #ffffff;
}

/* Hide MathLive default shadow-root buttons to keep our custom UI clean */
math-field::part(virtual-keyboard-toggle),
math-field::part(menu-toggle) {
  display: none !important;
}

@keyframes mathKeyboardSlideIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Virtual Keyboard Area */
#keyboard-container {
  display: none;
  width: 100%;
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding-bottom: var(--safe-area-bottom);
  z-index: 35;
  flex-shrink: 0;
}

#keyboard-container.is-open {
  display: block;
}

#keyboard-container.is-open .math-keyboard {
  animation: mathKeyboardSlideIn 0.16s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Default / Light Virtual Keyboard */
.math-keyboard {
  display: flex;
  flex-direction: column;
  width: 100%;
  max-width: 740px;
  margin: 0 auto;
  background: #f1f5f9;
  user-select: none;
  border-left: 1px solid var(--border-color);
  border-right: 1px solid var(--border-color);
}

.math-keyboard-tabs {
  display: flex;
  align-items: center;
  background: #e2e8f0;
  border-bottom: 1px solid #cbd5e1;
  padding: 4px 6px;
  gap: 4px;
}

.math-tab-btn {
  background: transparent;
  border: none;
  color: #475569;
  padding: 5px 14px;
  font-size: 13px;
  font-weight: 600;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.math-tab-btn.active {
  background: #ffffff;
  color: #0f172a;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
}

.math-tab-paste {
  margin-left: auto;
  background: rgba(37, 99, 235, 0.1);
  color: var(--accent-color);
  border: 1px solid rgba(37, 99, 235, 0.25);
  padding: 4px 10px;
  font-size: 12px;
}

.math-tab-paste:hover {
  background: rgba(37, 99, 235, 0.18);
}

.math-tab-dismiss {
  margin-left: 4px;
  font-size: 16px;
  padding: 4px 10px;
  color: #64748b;
}

.formula-bar-actions {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.formula-paste-btn {
  min-width: 38px;
  min-height: 38px;
  padding: 6px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-card);
  color: var(--text-secondary);
  flex-shrink: 0;
}

.formula-paste-btn:hover {
  border-color: var(--accent-color);
  color: var(--accent-color);
}

.paste-modal-hint {
  font-size: 12.5px;
  color: var(--text-secondary);
  line-height: 1.45;
}

.paste-equation-input {
  width: 100%;
  min-height: 44px;
  padding: 10px 12px;
  border-radius: 8px;
  border: 1px solid var(--border-strong);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 16px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  outline: none;
}

.paste-equation-input:focus {
  border-color: var(--accent-color);
  box-shadow: 0 0 0 1px var(--accent-color);
}

.paste-modal-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: flex-end;
}

.paste-action-btn {
  padding: 8px 14px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-primary);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
}

.paste-action-btn.primary {
  background: var(--accent-color);
  border-color: var(--accent-color);
  color: #ffffff;
}

.math-keyboard-grid {
  display: flex;
  flex-direction: column;
  padding: 6px;
  gap: 5px;
  background: #f8fafc;
}

.math-keyboard-row {
  display: flex;
  width: 100%;
  gap: 5px;
}

.math-key {
  flex: 1;
  min-width: 0;
  height: 39px;
  border-radius: 6px;
  border: 1px solid #cbd5e1;
  background: #ffffff;
  color: #0f172a;
  font-size: 15px;
  font-weight: 500;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.1s, transform 0.05s;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

.math-key:active {
  background: #e2e8f0;
}

.math-key-number {
  background: #f1f5f9;
  font-weight: 700;
}

.math-key-operator {
  background: #ffffff;
  color: #2563eb;
}

.math-key-action {
  background: #e2e8f0;
  color: #334155;
}

.math-key-accent {
  background: #2563eb;
  color: #ffffff;
  border-color: #1d4ed8;
  box-shadow: 0 1px 2px rgba(37, 99, 235, 0.25);
}

.math-key.math-key-pressed {
  background: #2563eb !important;
  color: #ffffff !important;
  transform: scale(0.92);
  box-shadow: 0 0 8px rgba(37, 99, 235, 0.5);
  transition: transform 0.06s ease, background 0.06s ease;
}

.math-key.math-key-context-active {
  border-color: #2563eb !important;
  background: rgba(37, 99, 235, 0.12) !important;
  color: #1d4ed8 !important;
  box-shadow: inset 0 0 0 1px #2563eb;
}

/* 2D Micro-Math Keycap Templates */
.math-key-template {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  font-family: inherit;
  font-size: 14px;
}

.math-key-frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  line-height: 1;
  font-size: 11px;
}

.math-key-frac .frac-bar {
  width: 14px;
  height: 1.5px;
  background-color: currentColor;
  margin: 1.5px 0;
  border-radius: 1px;
}

.math-key-frac .frac-box,
.math-key-root .root-box,
.math-key-power .power-box {
  display: inline-block;
  width: 8px;
  height: 8px;
  border: 1px dashed rgba(0, 0, 0, 0.45);
  border-radius: 2px;
}

.math-key-power {
  display: inline-flex;
  align-items: flex-start;
  font-size: 14px;
  line-height: 1;
}

.math-key-power .power-box {
  width: 7px;
  height: 7px;
  margin-top: -3px;
  margin-left: 1px;
}

.math-key-root {
  display: inline-flex;
  align-items: center;
  line-height: 1;
}

.math-key-root .root-box {
  width: 8px;
  height: 8px;
  margin-left: 1px;
  border-top: 1.5px solid currentColor;
}

/* Dark Virtual Keyboard (Scoped to .math-keyboard-dark and [data-theme="dark"]) */
.math-keyboard-dark,
[data-theme="dark"] .math-keyboard {
  background: #111827;
}

.math-keyboard-dark .math-keyboard-tabs,
[data-theme="dark"] .math-keyboard-tabs {
  background: #1f2937;
  border-bottom: 1px solid #374151;
}

.math-keyboard-dark .math-tab-btn,
[data-theme="dark"] .math-tab-btn {
  color: #9ca3af;
}

.math-keyboard-dark .math-tab-btn.active,
[data-theme="dark"] .math-tab-btn.active {
  background: #374151;
  color: #f9fafb;
  box-shadow: none;
}

.math-keyboard-dark .math-keyboard-grid,
[data-theme="dark"] .math-keyboard-grid {
  background: #0f172a;
}

.math-keyboard-dark .math-key,
[data-theme="dark"] .math-key {
  border: 1px solid #334155;
  background: #1e293b;
  color: #f8fafc;
  box-shadow: none;
}

.math-keyboard-dark .math-key:active,
[data-theme="dark"] .math-key:active {
  background: #475569;
}

.math-keyboard-dark .math-key-number,
[data-theme="dark"] .math-key-number {
  background: #334155;
  font-weight: 600;
}

.math-keyboard-dark .math-key-operator,
[data-theme="dark"] .math-key-operator {
  background: #1e293b;
  color: #60a5fa;
}

.math-keyboard-dark .math-key-action,
[data-theme="dark"] .math-key-action {
  background: #475569;
  color: #e2e8f0;
}

.math-keyboard-dark .math-key-accent,
[data-theme="dark"] .math-key-accent {
  background: #2563eb;
  color: #ffffff;
  border-color: #3b82f6;
  box-shadow: none;
}

.math-keyboard-dark .math-key.math-key-pressed,
[data-theme="dark"] .math-key.math-key-pressed {
  background: #3b82f6 !important;
  color: #ffffff !important;
  box-shadow: 0 0 10px rgba(59, 130, 246, 0.7);
}

.math-keyboard-dark .math-key.math-key-context-active,
[data-theme="dark"] .math-key.math-key-context-active {
  border-color: #60a5fa !important;
  background: rgba(59, 130, 246, 0.28) !important;
  color: #93c5fd !important;
  box-shadow: inset 0 0 0 1px #3b82f6;
}

.math-keyboard-dark .math-key-frac .frac-box,
.math-keyboard-dark .math-key-root .root-box,
.math-keyboard-dark .math-key-power .power-box,
[data-theme="dark"] .math-key-frac .frac-box,
[data-theme="dark"] .math-key-root .root-box,
[data-theme="dark"] .math-key-power .power-box {
  border: 1px dashed rgba(255, 255, 255, 0.6);
}

/* Export / Save / Paste Modal Dialogs */
.modal-backdrop {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--app-usable-height, 100vh);
  max-height: 100%;
  background: rgba(15, 23, 42, 0.45);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

[data-theme="dark"] .modal-backdrop {
  background: rgba(0, 0, 0, 0.7);
}

.export-modal {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 14px;
  width: 480px;
  max-width: 95vw;
  max-height: calc(var(--app-usable-height, 100vh) - 32px);
  overflow-y: auto;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.15);
  display: flex;
  flex-direction: column;
}

[data-theme="dark"] .export-modal {
  background: var(--bg-secondary);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
}

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

.modal-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
}

.modal-close-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 20px;
  line-height: 1;
}

.modal-body {
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.export-section-title {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.export-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.export-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 14px;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: all 0.15s ease;
  text-align: left;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.03);
}

.export-card:hover {
  border-color: var(--accent-color);
  background: rgba(37, 99, 235, 0.05);
}

[data-theme="dark"] .export-card {
  background: var(--bg-primary);
  box-shadow: none;
}

[data-theme="dark"] .export-card:hover {
  border-color: var(--accent-color);
  background: rgba(59, 130, 246, 0.08);
}

.export-card-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-primary);
}

.export-card-desc {
  font-size: 12px;
  color: var(--text-secondary);
}

.export-card-action {
  margin-top: 4px;
  font-size: 12px;
  font-weight: 600;
  color: var(--accent-color);
}

/* Toast Notification for Copy/Save actions */
.toast-notice {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  background: #10b981;
  color: #ffffff;
  padding: 10px 20px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 14px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.4);
  z-index: 200;
  transition: opacity 0.3s;
}

/* Responsive adjustments */

/* Adaptive Header Container Queries (responds to actual shell width across all screen sizes) */
@container app-shell (max-width: 960px) {
  .app-header {
    padding: 6px 10px;
    gap: 8px;
  }

  .app-title span {
    display: none;
  }

  .worksheet-status-btn {
    max-width: 175px;
    padding: 4px 8px;
  }

  .mode-tab-btn {
    padding: 5px 9px;
    font-size: 12.5px;
  }
}

@container app-shell (max-width: 820px) {
  .mode-label-full {
    display: none;
  }

  .mode-label-compact {
    display: inline;
  }

  .app-actions {
    gap: 2px;
  }

  .app-actions .icon-btn {
    padding: 6px;
  }
}

@container app-shell (max-width: 730px) {
  .action-secondary {
    display: none;
  }

  .icon-btn.btn-more-actions {
    display: inline-flex;
  }
}

@container app-shell (max-width: 640px) {
  .app-header {
    flex-wrap: wrap;
    padding: 6px 8px;
    gap: 6px;
  }

  .header-left {
    order: 1;
    flex: 1 1 0;
    min-width: 0;
    gap: 4px;
  }

  .app-title {
    display: none;
  }

  .worksheet-status-btn {
    max-width: 100%;
    padding: 4px 8px;
  }

  .app-actions {
    order: 2;
    flex: 0 0 auto;
    gap: 2px;
  }

  .app-header .icon-btn {
    min-width: 34px;
    min-height: 34px;
    padding: 6px;
  }

  .mode-tabs {
    order: 3;
    flex: 1 0 100%;
    width: 100%;
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    padding: 3px;
    gap: 2px;
  }

  .mode-tab-btn {
    width: 100%;
    padding: 6px 4px;
    font-size: 12px;
    text-align: center;
    overflow: hidden;
    text-overflow: ellipsis;
  }
}

@container app-shell (max-width: 440px) {
  .save-badge {
    width: 8px;
    height: 8px;
    min-width: 8px;
    padding: 0;
    font-size: 0;
    line-height: 0;
    border-radius: 50%;
  }

  .save-badge.saved {
    background: #10b981;
  }

  .save-badge.saving {
    background: #3b82f6;
  }

  .save-badge.dirty {
    background: #f59e0b;
  }

  .mode-tab-btn {
    font-size: 11.5px;
    padding: 6px 2px;
  }
}

/* Tablet (641px - 1024px) */
@media (max-width: 1024px) {
  :root {
    --math-expr-font-size: clamp(1.05rem, 0.95rem + 0.35vw, 1.1875rem);
    --math-editor-font-size: clamp(1.125rem, 1.02rem + 0.35vw, 1.3rem);
  }

  #expression-drawer {
    width: clamp(300px, 38vw, 360px);
  }

  .math-keyboard {
    max-width: 100%;
    border-left: none;
    border-right: none;
  }

  .math-key {
    height: 41px;
  }
}

/* Mobile (<= 640px) */
@media (max-width: 640px) {
  :root {
    --math-expr-font-size: 1.0625rem;
    --math-editor-font-size: 1.125rem;
    --math-result-font-size: 13px;
  }

  .export-grid {
    grid-template-columns: 1fr;
  }

  .mode-overlay {
    top: 10px;
    right: 10px;
    max-width: calc(100vw - 20px);
  }

  .floating-canvas-btn {
    bottom: 14px;
    right: 14px;
    width: 40px;
    height: 40px;
  }

  #math-input-bar {
    padding: 5px 6px;
    gap: 6px;
  }

  .math-keyboard-grid {
    padding: 5px;
    gap: 4px;
  }

  .math-keyboard-row {
    gap: 4px;
  }

  .math-key {
    height: 42px;
    font-size: 14px;
    padding: 0 2px;
  }

  .math-tab-btn {
    padding: 6px 12px;
  }
}

/* Mobile Portrait: bottom-docked expression sheet keeps graph visible above */
@media (max-width: 640px) and (min-height: 501px) {
  #expression-drawer {
    top: auto;
    bottom: 0;
    left: 0;
    right: 0;
    width: 100%;
    max-width: 100%;
    height: min(44vh, 300px);
    max-height: 56%;
    border-right: none;
    border-top: 1px solid var(--border-color);
    border-radius: 14px 14px 0 0;
    box-shadow: 0 -6px 24px rgba(0, 0, 0, 0.12);
  }

  [data-theme="dark"] #expression-drawer {
    box-shadow: 0 -8px 28px rgba(0, 0, 0, 0.45);
  }

  #expression-drawer.collapsed {
    transform: translateY(105%);
  }

  #viewport-container.drawer-open .floating-canvas-btn {
    bottom: calc(min(44vh, 300px) + 12px);
  }

  .add-expr-menu {
    max-height: min(300px, 48vh);
  }
}

/* Mobile / Compact Landscape */
@media (max-width: 900px) and (max-height: 500px) {
  .app-header {
    flex-wrap: nowrap;
    min-height: 44px;
    padding: 4px 8px;
    gap: 6px;
  }

  .header-left {
    order: 1;
  }

  .mode-tabs {
    order: 2;
    flex: 0 1 auto;
    width: auto;
    display: flex;
  }

  .app-actions {
    order: 3;
  }

  .mode-tab-btn {
    width: auto;
    padding: 4px 8px;
    font-size: 12px;
  }

  #expression-drawer {
    width: min(320px, 46vw);
    max-width: 60vw;
    height: 100%;
    top: 0;
    left: 0;
    border-radius: 0;
  }

  .math-key {
    height: 33px;
    font-size: 13.5px;
  }

  .math-keyboard-tabs {
    padding: 2px 6px;
  }

  .math-tab-btn {
    padding: 4px 10px;
    font-size: 12px;
  }

  .add-expr-menu {
    max-height: calc(100vh - 130px);
  }
}

/* Larger touch targets for coarse pointer devices (Android / iOS) */
@media (pointer: coarse) {

  .visibility-btn,
  .duplicate-btn,
  .delete-btn {
    min-width: 32px;
    min-height: 32px;
  }

  .btn-add-expr-trigger {
    min-height: 42px;
  }

  .btn-add {
    padding: 9px 10px;
    min-height: 44px;
  }

  .formula-paste-btn,
  .keyboard-toggle-btn {
    min-width: 42px;
    min-height: 40px;
  }
}