/* Economics Textbook — Shared Stylesheet */

:root {
  /* Semantic graph colors (unchanged across themes) */
  --color-demand: #2563eb;
  --color-supply: #dc2626;
  --color-msc: #991b1b;
  --color-equilibrium: #16a34a;
  --color-surplus-cs: rgba(37, 99, 235, 0.15);
  --color-surplus-ps: rgba(220, 38, 38, 0.15);
  --color-dwl: rgba(250, 204, 21, 0.25);
  --color-tax: rgba(139, 92, 246, 0.15);

  /* Light theme (default) */
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-text: #1a1a2e;
  --color-text-secondary: #475569;
  --color-heading: #0f172a;
  --color-accent: #2563eb;
  --color-border: #e2e8f0;
  --color-practice: #059669;
  --color-apply: #d97706;
  --color-challenge: #dc2626;

  /* Component colors — light */
  --color-definition-bg: #f8fafc;
  --color-definition-border: #2563eb;
  --color-example-bg: #f0fdf4;
  --color-example-border: #059669;
  --color-thread-bg: #fffbeb;
  --color-thread-border: #fbbf24;
  --color-thread-heading: #92400e;
  --color-summary-bg: #eff6ff;
  --color-summary-border: #bfdbfe;
  --color-equation-bg: #f8fafc;
  --color-eq-label: #64748b;

  /* Graph colors */
  --graph-bg: #ffffff;
  --graph-grid: #e2e8f0;
  --graph-text: #1a1a2e;

  /* Slider colors */
  --color-slider-track: #cbd5e1;
  --color-slider-thumb: #2563eb;

  /* Table colors */
  --color-table-header-bg: #f8fafc;
  --color-table-hover: #f1f5f9;

  /* Exercise badge colors — light */
  --color-practice-badge-bg: #d1fae5;
  --color-apply-badge-bg: #fef3c7;
  --color-challenge-badge-bg: #fee2e2;

  /* Nav hover */
  --color-nav-hover: #e2e8f0;

  /* Eq readout */
  --color-eq-readout-bg: #f0fdf4;
  --color-eq-readout-border: #bbf7d0;
  --color-eq-readout-strong: #16a34a;

  /* Figure container */
  --color-figure-border: #e8e8e8;
  --color-figure-shadow: rgba(0,0,0,0.05);
}

/* Dark theme */
[data-theme="dark"] {
  --color-bg: #0f172a;
  --color-bg-alt: #1e293b;
  --color-text: #e2e8f0;
  --color-text-secondary: #94a3b8;
  --color-heading: #f1f5f9;
  --color-accent: #60a5fa;
  --color-border: #334155;
  --color-practice: #22c55e;
  --color-apply: #f59e0b;
  --color-challenge: #f87171;

  --color-definition-bg: #1e293b;
  --color-definition-border: #60a5fa;
  --color-example-bg: rgba(20, 83, 45, 0.13);
  --color-example-border: #22c55e;
  --color-thread-bg: rgba(120, 53, 15, 0.13);
  --color-thread-border: #f59e0b;
  --color-thread-heading: #fbbf24;
  --color-summary-bg: #1e3a5f;
  --color-summary-border: #3b82f6;
  --color-equation-bg: #1e293b;
  --color-eq-label: #94a3b8;

  --graph-bg: #0f172a;
  --graph-grid: #334155;
  --graph-text: #e2e8f0;

  --color-slider-track: #334155;
  --color-slider-thumb: #60a5fa;

  --color-table-header-bg: #1e293b;
  --color-table-hover: #1e293b;

  --color-practice-badge-bg: rgba(20, 83, 45, 0.4);
  --color-apply-badge-bg: rgba(120, 53, 15, 0.4);
  --color-challenge-badge-bg: rgba(127, 29, 29, 0.4);

  --color-nav-hover: #334155;

  --color-eq-readout-bg: rgba(20, 83, 45, 0.2);
  --color-eq-readout-border: #166534;
  --color-eq-readout-strong: #22c55e;

  --color-figure-border: #334155;
  --color-figure-shadow: rgba(0,0,0,0.3);

  /* Adjust semantic graph colors for dark background legibility */
  --color-demand: #60a5fa;
  --color-supply: #f87171;
  --color-msc: #fca5a5;
  --color-equilibrium: #4ade80;
  --color-surplus-cs: rgba(96, 165, 250, 0.2);
  --color-surplus-ps: rgba(248, 113, 113, 0.2);
  --color-dwl: rgba(250, 204, 21, 0.2);
  --color-tax: rgba(167, 139, 250, 0.2);
}

/* Reading theme */
[data-theme="reading"] {
  --color-bg: #f5f0e6;
  --color-bg-alt: #ebe5d6;
  --color-text: #2c2416;
  --color-text-secondary: #5c5245;
  --color-heading: #1a1207;
  --color-accent: #1e5a8a;
  --color-border: #d4cdc0;
  --color-practice: #4a7c3f;
  --color-apply: #8a6d2b;
  --color-challenge: #9a3030;

  --color-definition-bg: #eae4d5;
  --color-definition-border: #1e5a8a;
  --color-example-bg: #e8eed8;
  --color-example-border: #4a7c3f;
  --color-thread-bg: #f5eedd;
  --color-thread-border: #c9a84c;
  --color-thread-heading: #7a5c1a;
  --color-summary-bg: #e0e8d8;
  --color-summary-border: #7a9a6a;
  --color-equation-bg: #f0ebe0;
  --color-eq-label: #5c5245;

  --graph-bg: #faf6ee;
  --graph-grid: #d4cdc0;
  --graph-text: #2c2416;

  --color-slider-track: #d4cdc0;
  --color-slider-thumb: #1e5a8a;

  --color-table-header-bg: #ebe5d6;
  --color-table-hover: #e5dfd0;

  --color-practice-badge-bg: #d4e8c8;
  --color-apply-badge-bg: #f0e4c8;
  --color-challenge-badge-bg: #f0d4d4;

  --color-nav-hover: #ddd7c8;

  --color-eq-readout-bg: #e8eed8;
  --color-eq-readout-border: #b8ccaa;
  --color-eq-readout-strong: #4a7c3f;

  --color-figure-border: #d4cdc0;
  --color-figure-shadow: rgba(0,0,0,0.06);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: 'Georgia', 'Times New Roman', serif;
  font-size: 18px;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  max-width: 820px;
  margin: 0 auto;
  padding: 40px 30px 80px;
}

/* Headings */
h1 {
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 2.2em;
  font-weight: 700;
  color: var(--color-heading);
  margin: 0 0 8px;
  padding-bottom: 12px;
  border-bottom: 3px solid var(--color-accent);
}

h1 .chapter-num {
  display: block;
  font-size: 0.45em;
  font-weight: 400;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: 4px;
}

h2 {
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 1.5em;
  font-weight: 600;
  color: var(--color-heading);
  margin: 48px 0 16px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--color-border);
}

h3 {
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 1.2em;
  font-weight: 600;
  color: var(--color-heading);
  margin: 32px 0 12px;
}

h4 {
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 1.05em;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin: 24px 0 8px;
}

/* Paragraphs */
p { margin: 0 0 16px; }

/* Links */
a { color: var(--color-accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Definition terms */
.definition {
  margin: 20px 0;
  padding: 16px 20px;
  background: var(--color-definition-bg);
  border-left: 4px solid var(--color-definition-border);
  border-radius: 0 4px 4px 0;
}

.definition strong { color: var(--color-heading); }

/* Equations — numbered */
.equation {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 24px 0;
  padding: 12px 20px;
  background: var(--color-equation-bg);
  border-radius: 4px;
}

.equation .eq-label {
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.85em;
  color: var(--color-eq-label);
  white-space: nowrap;
  margin-left: 20px;
}

/* Figures / Graphs */
.figure-container {
  margin: 32px 0;
  padding: 12px;
  border: 1px solid var(--color-figure-border);
  border-radius: 6px;
  box-shadow: 0 1px 4px var(--color-figure-shadow);
}

.figure-container .plotly-graph-div {
  margin: 0 auto;
}

/* Prevent Plotly containers from collapsing to 0 height on Plotly.react() re-render */
.figure-container .js-plotly-plot {
  min-height: 400px;
}

.figure-caption {
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.9em;
  color: var(--color-text-secondary);
  margin-top: 8px;
  padding: 0 12px;
  line-height: 1.5;
}

.figure-caption strong {
  color: var(--color-heading);
}

/* ── Interactive Components (shared across chapters) ────────────────── */

/* Slider containers */
.slider-container {
  margin: 16px 0 8px;
  padding: 16px 20px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-family: 'Helvetica Neue', sans-serif;
}

.slider-container label {
  display: block;
  font-weight: 600;
  margin-bottom: 8px;
  font-size: 0.95em;
  color: var(--color-heading);
}

.slider-container input[type="range"] {
  width: 100%;
  height: 6px;
  -webkit-appearance: none;
  appearance: none;
  background: var(--color-slider-track);
  border-radius: 3px;
  outline: none;
  cursor: pointer;
}

.slider-container input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--color-slider-thumb);
  cursor: grab;
  border: 2px solid var(--color-bg);
  box-shadow: 0 1px 3px rgba(0,0,0,0.3);
}

.slider-container input[type="range"]::-webkit-slider-thumb:active {
  cursor: grabbing;
  background: var(--color-accent);
}

.slider-readout {
  display: flex;
  justify-content: space-between;
  margin-top: 6px;
  font-size: 0.85em;
  color: var(--color-text-secondary);
}

.slider-value {
  font-size: 1.1em;
  font-weight: 700;
  color: var(--color-accent);
}

.slider-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 24px;
}

.slider-group .slider-container {
  margin: 8px 0;
}

/* Equation readout */
.eq-readout {
  margin: 12px 0 4px;
  padding: 12px 16px;
  background: var(--color-example-bg);
  border-radius: 6px;
  border: 1px solid var(--color-example-border);
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.95em;
  line-height: 1.8;
}

.eq-readout strong {
  color: var(--color-practice);
}

/* Toggle buttons (used in Ch4, 7, 12, 15, 18) */
.toggle-container {
  display: flex;
  gap: 8px;
  margin: 12px 0;
  flex-wrap: wrap;
  align-items: center;
}

.toggle-container label {
  font-family: 'Helvetica Neue', sans-serif;
  font-weight: 600;
  font-size: 0.95em;
  color: var(--color-heading);
}

.toggle-btn,
.toggle-container button {
  padding: 6px 16px;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  background: var(--color-bg-alt);
  color: var(--color-text);
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.88em;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}

.toggle-btn:hover,
.toggle-container button:hover {
  background: var(--color-border);
}

.toggle-btn.active,
.toggle-container button.active {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

/* Interactive sections (used in Ch9, 11, 16, 17, 18) */
.interactive-section {
  margin: 24px 0;
  padding: 20px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 8px;
}

.interactive-section:last-of-type {
  margin-bottom: 32px;
}

.interactive-section h3 {
  margin-top: 0;
}

/* Multi-panel layouts */
.dual-panel,
.two-panel,
.side-by-side {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 16px 0;
}

.dual-panel > div,
.two-panel > div,
.side-by-side > div {
  min-width: 0;
}

.three-panel {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 16px;
  margin: 16px 0;
}

.dual-panel > .figure-container {
  margin: 0;
}

/* Panel labels (Ch8, 13) */
.panel-label {
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.85em;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 4px;
  display: inline-block;
  margin-bottom: 8px;
}

.panel-label.fiscal {
  background: var(--color-summary-bg);
  color: var(--color-accent);
}

.panel-label.monetary {
  background: #fef2f2;
  color: var(--color-challenge);
}

/* Warning readouts (Ch14, 15) */
.warning-readout {
  margin: 12px 0 4px;
  padding: 12px 16px;
  background: var(--color-thread-bg);
  border: 1px solid var(--color-thread-border);
  border-radius: 6px;
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.95em;
}

/* Click hints */
.click-hint {
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.85em;
  color: var(--color-text-secondary);
  font-style: italic;
  margin: 4px 0 8px;
}

/* Interactive buttons (Ch11, 17) */
.btn {
  padding: 8px 16px;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.9em;
  cursor: pointer;
  transition: background 0.15s;
}

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

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

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

.btn.run:hover {
  opacity: 0.9;
}

@media (max-width: 600px) {
  .dual-panel, .two-panel, .side-by-side {
    grid-template-columns: 1fr;
  }
  .three-panel {
    grid-template-columns: 1fr;
  }
  .slider-grid {
    grid-template-columns: 1fr;
  }
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 0.95em;
}

th {
  background: var(--color-table-header-bg);
  font-family: 'Helvetica Neue', sans-serif;
  font-weight: 600;
  text-align: left;
  padding: 10px 14px;
  border-bottom: 2px solid var(--color-border);
}

td {
  padding: 8px 14px;
  border-bottom: 1px solid var(--color-border);
}

tr:hover { background: var(--color-table-hover); }

/* Examples */
.example {
  margin: 24px 0;
  padding: 20px 24px;
  background: var(--color-example-bg);
  border-left: 4px solid var(--color-example-border);
  border-radius: 0 4px 4px 0;
}

.example-title {
  font-family: 'Helvetica Neue', sans-serif;
  font-weight: 700;
  color: var(--color-practice);
  margin-bottom: 8px;
}

/* Thread examples */
.thread-example {
  margin: 32px 0;
  padding: 24px;
  background: var(--color-thread-bg);
  border: 1px solid var(--color-thread-border);
  border-radius: 6px;
}

.thread-example h3 {
  font-family: 'Helvetica Neue', sans-serif;
  color: var(--color-thread-heading);
  margin-top: 0;
}

/* Exercises */
.exercises { margin-top: 48px; }

.exercises h3 {
  font-family: 'Helvetica Neue', sans-serif;
  display: inline-block;
  padding: 4px 12px;
  border-radius: 4px;
  font-size: 1em;
  margin-bottom: 16px;
}

.exercises h3.practice { background: var(--color-practice-badge-bg); color: var(--color-practice); }
.exercises h3.apply { background: var(--color-apply-badge-bg); color: var(--color-apply); }
.exercises h3.challenge { background: var(--color-challenge-badge-bg); color: var(--color-challenge); }

.exercises ol { padding-left: 24px; }
.exercises li { margin-bottom: 16px; }

/* Key equations summary table */
.key-equations table {
  font-size: 0.9em;
}

.key-equations td:first-child {
  font-family: 'Courier New', monospace;
  font-weight: 600;
  white-space: nowrap;
  color: var(--color-accent);
}

/* Summary box */
.summary {
  margin: 40px 0;
  padding: 24px;
  background: var(--color-summary-bg);
  border-radius: 6px;
  border: 1px solid var(--color-summary-border);
}

.summary h2 { border-bottom: none; margin-top: 0; color: var(--color-accent); }
.summary ul { padding-left: 20px; }
.summary li { margin-bottom: 10px; }

/* Learning objectives */
.objectives {
  margin: 20px 0 32px;
  padding: 16px 24px;
  background: var(--color-bg-alt);
  border-radius: 6px;
}

.objectives ol { padding-left: 20px; }
.objectives li { margin-bottom: 6px; font-size: 0.95em; }

/* Navigation */
.nav {
  display: flex;
  justify-content: space-between;
  margin-top: 60px;
  padding-top: 20px;
  border-top: 2px solid var(--color-border);
  font-family: 'Helvetica Neue', sans-serif;
  font-size: 0.9em;
}

.nav a {
  padding: 8px 16px;
  background: var(--color-bg-alt);
  border-radius: 4px;
  border: 1px solid var(--color-border);
}

.nav a:hover {
  background: var(--color-nav-hover);
  text-decoration: none;
}

/* MathJax overrides */
mjx-container[display="true"] { margin: 16px 0 !important; }
mjx-container { color: var(--color-text) !important; }

/* Theme toggle component */
.theme-toggle {
  position: fixed;
  top: 12px;
  right: 16px;
  z-index: 10000;
  display: flex;
  gap: 2px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 3px;
  font-family: 'Helvetica Neue', Arial, sans-serif;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.theme-toggle button {
  border: none;
  background: transparent;
  padding: 5px 10px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 14px;
  color: var(--color-text-secondary);
  transition: background 0.15s, color 0.15s;
  line-height: 1;
}

.theme-toggle button:hover {
  background: var(--color-border);
}

.theme-toggle button.active {
  background: var(--color-accent);
  color: #ffffff;
}

/* ═══════════════════════════════════════════════════════════════════════
   Navigation System
   ═══════════════════════════════════════════════════════════════════════ */

/* Reading progress bar — thin bar at very top of viewport */
.nav-progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 4px;
  width: 0%;
  background: var(--color-accent);
  z-index: 1100;
  pointer-events: none;
  transition: none;
}

/* Sticky header */
.nav-header {
  position: fixed;
  top: 4px;
  left: 0;
  right: 0;
  height: 48px;
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 0.85em;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.08);
}

.nav-header-left,
.nav-header-right {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

/* Header links */
.nav-home,
.nav-prev,
.nav-next {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 6px 12px;
  border-radius: 4px;
  color: var(--color-text);
  text-decoration: none;
  white-space: nowrap;
  min-height: 36px;
  transition: background 0.15s;
}

.nav-home:hover,
.nav-prev:hover,
.nav-next:hover {
  background: var(--color-bg-alt);
  text-decoration: none;
}

.nav-home-icon {
  font-size: 1.2em;
}

.nav-disabled {
  opacity: 0.35;
  pointer-events: none;
}

/* Chapter title in header */
.nav-title {
  font-weight: 600;
  color: var(--color-heading);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  flex: 1;
  text-align: center;
  padding: 0 8px;
  min-width: 0;
}

/* Placeholder slots for theme toggle and language selector */
.nav-theme-slot,
.nav-lang-slot {
  display: flex;
  align-items: center;
}

/* Sidebar toggle (hamburger) button */
.nav-sidebar-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 4px;
  width: 36px;
  height: 36px;
  padding: 6px;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  cursor: pointer;
  flex-shrink: 0;
}

.nav-sidebar-toggle:hover {
  background: var(--color-bg-alt);
}

.hamburger-line {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
}

/* Body offset to prevent content being hidden behind header */
body.nav-sidebar-visible {
  margin-left: 260px;
  max-width: calc(820px);
}

/* Sidebar TOC */
.nav-sidebar {
  position: fixed;
  top: 52px;
  left: 0;
  width: 260px;
  height: calc(100vh - 52px);
  overflow-y: auto;
  z-index: 900;
  background: var(--color-bg);
  border-right: 1px solid var(--color-border);
  transform: translateX(-260px);
  transition: transform 0.25s ease;
  padding: 16px 0;
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 0.85em;
}

.nav-sidebar.expanded {
  transform: translateX(0);
}

/* Sidebar tabs */
.nav-sidebar-tabs {
  display: flex;
  border-bottom: 1px solid var(--color-border);
  margin: 0 0 4px;
  padding: 0 8px;
}

.nav-sidebar-tab {
  flex: 1;
  padding: 8px 4px;
  border: none;
  background: none;
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  font-size: 0.8em;
  font-weight: 600;
  color: var(--color-text-secondary);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: color 0.15s, border-color 0.15s;
  text-align: center;
}

.nav-sidebar-tab:hover {
  color: var(--color-text);
}

.nav-sidebar-tab.active {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.nav-sidebar-panel {
  display: none;
}

.nav-sidebar-panel.active {
  display: block;
}

/* Chapter list items */
.nav-toc-chapter a {
  padding: 5px 16px 5px 20px;
}

.nav-toc-chapter.current {
  background: var(--color-bg-alt);
}

/* TOC list */
.nav-toc {
  list-style: none;
  padding: 0;
  margin: 0;
}

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

.nav-toc a {
  display: block;
  padding: 6px 16px 6px 20px;
  color: var(--color-text-secondary);
  text-decoration: none;
  border-left: 3px solid transparent;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
  line-height: 1.4;
}

.nav-toc a:hover {
  background: var(--color-bg-alt);
  color: var(--color-text);
  text-decoration: none;
}

.nav-toc a.active {
  border-left-color: var(--color-accent);
  background: var(--color-bg-alt);
  color: var(--color-accent);
  font-weight: 600;
}

.nav-toc-h3 a {
  padding-left: 36px;
  font-size: 0.92em;
}

/* Sidebar overlay for mobile */
.nav-sidebar-overlay {
  display: none;
  position: fixed;
  top: 52px;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.4);
  z-index: 850;
}

.nav-sidebar-overlay.visible {
  display: block;
}

/* ── Desktop (>= 768px) ────────────────────────────────────────────── */
@media (min-width: 768px) {
  /* Pad top of body for fixed header + progress bar */
  body {
    padding-top: 72px;
  }

  .nav-prev .nav-link-text,
  .nav-next .nav-link-text {
    display: inline;
  }
}

/* ── Mobile (< 768px) ──────────────────────────────────────────────── */
@media (max-width: 767px) {
  body {
    padding-top: 64px;
  }

  /* Never offset body for sidebar on mobile */
  body.nav-sidebar-visible {
    margin-left: 0;
    max-width: none;
  }

  .nav-header {
    padding: 0 8px;
  }

  /* Hide text labels on prev/next */
  .nav-link-text {
    display: none;
  }

  .nav-home-text {
    display: none;
  }

  /* Ensure touch targets are 44x44 */
  .nav-home,
  .nav-prev,
  .nav-next,
  .nav-sidebar-toggle {
    min-width: 44px;
    min-height: 44px;
    justify-content: center;
  }

  /* Sidebar as full-height overlay */
  .nav-sidebar {
    width: 100%;
    transform: translateX(-100%);
  }

  .nav-sidebar.open {
    transform: translateX(0);
  }

  /* Don't use .expanded on mobile */
  .nav-sidebar.expanded {
    transform: translateX(-100%);
  }

  .nav-sidebar.expanded.open {
    transform: translateX(0);
  }

  .nav-title {
    font-size: 0.8em;
  }
}

/* ═══════════════════════════════════════════════════════════════════════
   Media Player System
   ═══════════════════════════════════════════════════════════════════════ */

/* Container — card style matching figure-container */
.media-player {
  margin: 32px 0;
  padding: 0;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.05);
  overflow: hidden;
  background: var(--color-bg);
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
}

/* Title bar (label + minimize button) */
.media-title-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 14px;
  background: var(--color-bg-alt);
  border-bottom: 1px solid var(--color-border);
  font-size: 0.85em;
  font-weight: 600;
  color: var(--color-text-secondary, #475569);
}

.media-label {
  display: flex;
  align-items: center;
  gap: 6px;
}

/* Shared button reset */
.media-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: none;
  background: transparent;
  cursor: pointer;
  color: var(--color-text);
  border-radius: 4px;
  padding: 4px;
  transition: background 0.15s;
}

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

/* Controls bar (shared audio + video) */
.media-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
}

/* Play button */
.media-play-btn {
  width: 36px;
  height: 36px;
  flex-shrink: 0;
  border-radius: 50%;
  background: var(--color-accent);
  color: #ffffff;
}

.media-play-btn:hover {
  background: var(--color-accent);
  opacity: 0.85;
}

/* Progress bar */
.media-progress-wrap {
  flex: 1;
  height: 8px;
  background: var(--color-border);
  border-radius: 4px;
  position: relative;
  cursor: pointer;
  min-width: 60px;
}

.media-progress-bar {
  height: 100%;
  background: var(--color-accent);
  border-radius: 4px;
  width: 0%;
  transition: width 0.1s linear;
  pointer-events: none;
}

/* Section markers on progress bar */
.media-marker {
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--color-heading);
  border: 2px solid var(--color-bg);
  cursor: pointer;
  z-index: 2;
}

.media-marker:hover {
  transform: translate(-50%, -50%) scale(1.3);
}

/* Time display */
.media-time {
  font-size: 0.8em;
  color: var(--color-text-secondary, #475569);
  white-space: nowrap;
  min-width: 80px;
  text-align: center;
  font-variant-numeric: tabular-nums;
}

/* Speed selector */
.media-speed {
  font-size: 0.8em;
  padding: 3px 6px;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-bg);
  color: var(--color-text);
  cursor: pointer;
  font-family: inherit;
}

.media-speed:focus {
  outline: 2px solid var(--color-accent);
  outline-offset: 1px;
}

/* Minimize button */
.media-minimize-btn {
  color: var(--color-text-secondary, #475569);
}

/* Audio minimized state (when floating) */
.media-audio-minimized .media-controls {
  opacity: 0.4;
  pointer-events: none;
}

.media-audio-minimized::after {
  content: 'Playing in mini-player';
  display: block;
  text-align: center;
  padding: 8px;
  font-size: 0.8em;
  color: var(--color-text-secondary, #475569);
  font-style: italic;
}

/* ── Video player ────────────────────────────────────────────────────── */

.media-video-wrap {
  position: relative;
  background: #000;
}

.media-video-wrap video {
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: contain;
  background: #000;
}

.media-video-controls {
  background: rgba(0, 0, 0, 0.6);
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 8px 12px;
  opacity: 0;
  transition: opacity 0.25s;
}

.media-video-wrap:hover .media-video-controls,
.media-video-wrap:focus-within .media-video-controls {
  opacity: 1;
}

.media-video-controls .media-play-btn {
  width: 28px;
  height: 28px;
}

.media-video-controls .media-time {
  color: rgba(255,255,255,0.8);
  font-size: 0.75em;
  min-width: 70px;
}

.media-video-controls .media-progress-wrap {
  height: 5px;
}

.media-video-controls .media-progress-bar {
  background: var(--color-accent);
}

/* Volume slider */
.media-vol-btn {
  color: #fff;
}

.media-vol-slider {
  width: 60px;
  height: 4px;
  -webkit-appearance: none;
  appearance: none;
  background: rgba(255,255,255,0.3);
  border-radius: 2px;
  outline: none;
  cursor: pointer;
}

.media-vol-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: #ffffff;
  cursor: pointer;
}

.media-vol-slider::-moz-range-thumb {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: #ffffff;
  border: none;
  cursor: pointer;
}

/* Subtitle selector */
.media-sub-selector {
  position: relative;
}

.media-sub-btn {
  color: #fff;
}

.media-sub-menu {
  position: absolute;
  bottom: 100%;
  right: 0;
  margin-bottom: 6px;
  display: flex;
  flex-direction: column;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  overflow: hidden;
  min-width: 80px;
  z-index: 10;
}

.media-sub-option {
  border: none;
  background: transparent;
  padding: 6px 14px;
  text-align: left;
  cursor: pointer;
  font-size: 0.8em;
  font-family: inherit;
  color: var(--color-text);
}

.media-sub-option:hover {
  background: var(--color-bg-alt);
}

/* Fullscreen button */
.media-fs-btn {
  color: #fff;
}

/* ── Floating mini-player ────────────────────────────────────────────── */

.media-mini-player {
  position: fixed;
  bottom: 16px;
  right: 16px;
  z-index: 950;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  box-shadow: 0 4px 16px rgba(0,0,0,0.12);
  font-family: 'Helvetica Neue', 'Arial', sans-serif;
  max-width: 320px;
  min-width: 240px;
}

.media-mini-player .mini-play-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  flex-shrink: 0;
  border: none;
  border-radius: 50%;
  background: var(--color-accent);
  color: #ffffff;
  cursor: pointer;
  padding: 0;
}

.media-mini-player .mini-play-btn:hover {
  opacity: 0.85;
}

.mini-progress-wrap {
  flex: 1;
  height: 4px;
  background: var(--color-border);
  border-radius: 2px;
  cursor: pointer;
  position: relative;
  min-width: 50px;
}

.mini-progress-bar {
  height: 100%;
  background: var(--color-accent);
  border-radius: 2px;
  width: 0%;
  pointer-events: none;
}

.mini-time {
  font-size: 0.75em;
  color: var(--color-text-secondary, #475569);
  white-space: nowrap;
  font-variant-numeric: tabular-nums;
  min-width: 32px;
}

.mini-restore-btn,
.mini-close-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  flex-shrink: 0;
  border: none;
  background: transparent;
  cursor: pointer;
  color: var(--color-text-secondary, #475569);
  border-radius: 4px;
  padding: 0;
}

.mini-restore-btn:hover,
.mini-close-btn:hover {
  background: var(--color-border);
}

/* ── "Coming soon" placeholder ───────────────────────────────────────── */

.media-placeholder {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 24px 20px;
  background: var(--color-bg-alt);
  border-radius: 6px;
  color: var(--color-text-secondary, #475569);
}

.media-placeholder-icon {
  flex-shrink: 0;
  opacity: 0.5;
  display: flex;
  align-items: center;
  justify-content: center;
}

.media-placeholder-icon svg {
  stroke: currentColor;
}

.media-placeholder-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.media-placeholder-text strong {
  font-size: 0.95em;
  color: var(--color-text);
}

.media-placeholder-text span {
  font-size: 0.85em;
  font-style: italic;
}

/* ── Media player responsive ─────────────────────────────────────────── */

@media (max-width: 600px) {
  .media-controls {
    flex-wrap: wrap;
    gap: 6px;
    padding: 8px 10px;
  }

  .media-time {
    font-size: 0.7em;
    min-width: 60px;
  }

  .media-mini-player {
    right: 8px;
    bottom: 8px;
    max-width: 280px;
    min-width: 200px;
    padding: 8px 10px;
  }

  .media-vol-slider {
    width: 40px;
  }
}

/* ── Media player print hide ─────────────────────────────────────────── */

@media print {
  .media-player,
  .media-mini-player {
    display: none;
  }
}

/* Print styles — always use light theme */
@media print {
  :root,
  [data-theme="dark"],
  [data-theme="reading"] {
    --color-bg: #ffffff;
    --color-bg-alt: #f8fafc;
    --color-text: #1a1a2e;
    --color-text-secondary: #475569;
    --color-heading: #0f172a;
    --color-accent: #2563eb;
    --color-border: #e2e8f0;
    --color-practice: #059669;
    --color-apply: #d97706;
    --color-challenge: #dc2626;
    --color-definition-bg: #f8fafc;
    --color-definition-border: #2563eb;
    --color-example-bg: #f0fdf4;
    --color-example-border: #059669;
    --color-thread-bg: #fffbeb;
    --color-thread-border: #fbbf24;
    --color-thread-heading: #92400e;
    --color-summary-bg: #eff6ff;
    --color-summary-border: #bfdbfe;
    --color-equation-bg: #f8fafc;
    --color-eq-label: #64748b;
    --graph-bg: #ffffff;
    --graph-grid: #e2e8f0;
    --graph-text: #1a1a2e;
    --color-table-header-bg: #f8fafc;
    --color-table-hover: #f1f5f9;
    --color-figure-border: #e8e8e8;
    --color-figure-shadow: rgba(0,0,0,0.05);
    --color-practice-badge-bg: #d1fae5;
    --color-apply-badge-bg: #fef3c7;
    --color-challenge-badge-bg: #fee2e2;
    --color-nav-hover: #e2e8f0;
    --color-demand: #2563eb;
    --color-supply: #dc2626;
    --color-msc: #991b1b;
    --color-equilibrium: #16a34a;
  }

  body { max-width: none; padding: 20px; font-size: 12pt; }
  .nav { display: none; }
  .nav-header, .nav-sidebar, .nav-progress-bar, .nav-sidebar-overlay { display: none; }
  body.nav-sidebar-visible { margin-left: 0; }
  .theme-toggle { display: none; }
  .plotly-graph-div { break-inside: avoid; }
  h2 { break-after: avoid; }
}

/* Responsive */
@media (max-width: 600px) {
  body { padding: 16px; font-size: 16px; }
  h1 { font-size: 1.6em; }
  h2 { font-size: 1.3em; }
  .theme-toggle { top: 8px; right: 8px; }
  .theme-toggle button { padding: 4px 8px; font-size: 12px; }
}