/* NCERT Plus One & Plus Two Chemistry — Modern Mobile-First Interactive Studio */
@import url("https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@500;700&family=Noto+Sans+Malayalam:wght@400;500;600;700&family=Plus+Jakarta+Sans:wght@600;700;800&display=swap");

:root {
  --font-display: "Plus Jakarta Sans", "Inter", "Segoe UI Variable", "Segoe UI", system-ui, -apple-system, sans-serif;
  --font-sans: "Inter", "Segoe UI Variable", "Segoe UI", system-ui, -apple-system, "Noto Sans Malayalam", "Nirmala UI", sans-serif;
  --font-ml: "Noto Sans Malayalam", "Manjari", "Nirmala UI", "Kartika", "Inter", sans-serif;
  --font-mono: "JetBrains Mono", "Cascadia Code", "Fira Code", Consolas, monospace;

  --bg: #f4f7fb;
  --bg-pattern: radial-gradient(1200px 420px at 15% -5%, rgba(37, 99, 235, 0.08), transparent 65%),
                radial-gradient(900px 360px at 85% 0%, rgba(124, 58, 237, 0.07), transparent 60%);
  --bg-elevated: #ffffff;
  --bg-glass: rgba(255, 255, 255, 0.86);
  --bg-soft: #eef2ff;
  --bg-story: linear-gradient(135deg, #fffbeb 0%, #fef3c7 100%);
  --border-story: #fcd34d;
  --bg-lab: linear-gradient(180deg, #f0fdf4 0%, #ecfdf5 100%);
  --border-lab: #86efac;
  --bg-trap: linear-gradient(135deg, #fef2f2 0%, #fee2e2 100%);
  --border-trap: #fca5a5;
  --bg-formula: #f8fafc;

  --text: #0f172a;
  --text-muted: #475569;
  --text-subtle: #64748b;
  --border: rgba(15, 23, 42, 0.09);
  --border-strong: rgba(15, 23, 42, 0.16);

  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-soft: #dbeafe;
  --primary-dark: #1e40af;
  --accent: #7c3aed;
  --accent-hover: #6d28d9;
  --accent-soft: #ede9fe;
  --success: #15803d;
  --success-soft: #dcfce7;
  --warning: #b45309;
  --danger: #dc2626;

  --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow-sm: 0 2px 8px rgba(15, 23, 42, 0.05), 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow-md: 0 10px 30px -6px rgba(15, 23, 42, 0.09);
  --shadow-lg: 0 20px 48px -12px rgba(15, 23, 42, 0.18);
  --radius: 18px;
  --player-h: 92px;
}

html.dark {
  --bg: #070b14;
  --bg-pattern: radial-gradient(1100px 440px at 15% -5%, rgba(59, 130, 246, 0.13), transparent 65%),
                radial-gradient(900px 380px at 88% 0%, rgba(139, 92, 246, 0.12), transparent 60%);
  --bg-elevated: #0f172a;
  --bg-glass: rgba(15, 23, 42, 0.88);
  --bg-soft: #17253e;
  --bg-story: linear-gradient(135deg, rgba(180, 83, 9, 0.18) 0%, rgba(120, 53, 15, 0.16) 100%);
  --border-story: rgba(245, 158, 11, 0.35);
  --bg-lab: linear-gradient(180deg, rgba(20, 83, 45, 0.24) 0%, rgba(15, 45, 30, 0.26) 100%);
  --border-lab: rgba(34, 197, 94, 0.34);
  --bg-trap: linear-gradient(135deg, rgba(153, 27, 27, 0.22) 0%, rgba(127, 29, 29, 0.18) 100%);
  --border-trap: rgba(248, 113, 113, 0.35);
  --bg-formula: #131d33;

  --text: #f1f5f9;
  --text-muted: #cbd5e1;
  --text-subtle: #94a3b8;
  --border: rgba(148, 163, 184, 0.14);
  --border-strong: rgba(148, 163, 184, 0.26);

  --primary: #3b82f6;
  --primary-hover: #60a5fa;
  --primary-soft: rgba(59, 130, 246, 0.18);
  --primary-dark: #93c5fd;
  --accent: #a78bfa;
  --accent-hover: #c4b5fd;
  --accent-soft: rgba(167, 139, 250, 0.16);
  --success: #4ade80;
  --success-soft: rgba(34, 197, 94, 0.16);
  --warning: #fbbf24;
  --danger: #f87171;

  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.32);
  --shadow-md: 0 12px 32px rgba(0, 0, 0, 0.45);
  --shadow-lg: 0 22px 54px rgba(0, 0, 0, 0.65);
}

*, *::before, *::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  padding: 0 0 calc(var(--player-h) + 28px) 0;
  background-color: var(--bg);
  background-image: var(--bg-pattern);
  background-attachment: fixed;
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.72;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

body.portal-body {
  padding-bottom: 48px;
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  letter-spacing: -0.02em;
  color: var(--text);
}

.ml-text {
  font-family: var(--font-ml);
  line-height: 1.88;
  font-size: 0.98rem;
}

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

a {
  color: var(--primary);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

button, input, select {
  font-family: inherit;
}

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

/* Custom subtle scrollbars */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: var(--border-strong);
  border-radius: 999px;
}

/* Top Navbar */
.topbar {
  position: sticky;
  top: 0;
  z-index: 60;
  background: var(--bg-glass);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  border-bottom: 1px solid var(--border);
}

.topbar-inner {
  max-width: 1340px;
  margin: 0 auto;
  padding: 10px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

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

.brand-title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.96rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.nav-pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-height: 36px;
  padding: 6px 13px;
  border-radius: 999px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  font-size: 0.84rem;
  font-weight: 600;
  white-space: nowrap;
  cursor: pointer;
  transition: transform 0.15s ease, border-color 0.15s ease, background 0.15s ease, box-shadow 0.15s ease;
}

.nav-pill:hover {
  border-color: var(--primary);
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: var(--shadow-xs);
}

.nav-pill.primary {
  background: linear-gradient(135deg, var(--primary), #4f46e5);
  color: #fff;
  border-color: transparent;
}

.nav-pill.accent {
  background: var(--accent-soft);
  color: var(--accent);
  border-color: color-mix(in srgb, var(--accent) 32%, transparent);
}

.top-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.mobile-menu-btn {
  display: none;
}

.mobile-close-drawer {
  display: none;
}

.drawer-backdrop {
  display: none;
}

.read-progress-track {
  height: 3px;
  width: 100%;
  background: var(--border);
}

.read-progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--primary), var(--accent), #ec4899);
  transition: width 0.15s ease;
}

/* Desktop & Tablet Page Layout */
.page-shell {
  max-width: 1340px;
  margin: 22px auto;
  padding: 0 20px;
  display: grid;
  grid-template-columns: 290px minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}

/* Sidebar / Mobile Slide-Over Drawer */
.sidebar {
  position: sticky;
  top: 76px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow-sm);
  max-height: calc(100vh - var(--player-h) - 102px);
  overflow-y: auto;
}

.sidebar-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.sidebar-title {
  font-family: var(--font-display);
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--text-subtle);
  font-weight: 800;
  margin: 0;
}

.toc-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.toc-btn {
  width: 100%;
  text-align: left;
  padding: 9px 10px;
  border-radius: 12px;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.86rem;
  font-weight: 500;
  line-height: 1.4;
  cursor: pointer;
  display: flex;
  align-items: flex-start;
  gap: 9px;
  transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}

.toc-btn:hover {
  background: var(--bg-soft);
  color: var(--text);
}

.toc-btn.active {
  background: var(--primary-soft);
  color: var(--primary-dark);
  border-color: color-mix(in srgb, var(--primary) 30%, transparent);
  font-weight: 700;
}

.toc-btn.done .toc-dot {
  background: var(--success);
  color: #fff;
}

.toc-dot {
  flex-shrink: 0;
  width: 22px;
  height: 22px;
  margin-top: 1px;
  border-radius: 999px;
  background: var(--border-strong);
  color: var(--text);
  font-size: 0.72rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

/* Main Column & Hero Card */
.main-col {
  display: flex;
  flex-direction: column;
  gap: 22px;
  min-width: 0;
}

.hero-card {
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg,
    color-mix(in srgb, var(--primary) 11%, var(--bg-elevated)) 0%,
    var(--bg-elevated) 55%,
    color-mix(in srgb, var(--accent) 10%, var(--bg-elevated)) 100%);
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 28px 30px;
  box-shadow: var(--shadow-md);
}

.chapter-kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 5px 13px;
  border-radius: 999px;
  background: var(--primary-soft);
  color: var(--primary-dark);
  font-family: var(--font-display);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.03em;
}

.hero-card h1 {
  margin: 14px 0 8px 0;
  font-size: clamp(1.5rem, 3.1vw, 2.35rem);
  font-weight: 800;
  line-height: 1.18;
}

.hero-subtitle {
  margin: 0 0 18px 0;
  color: var(--text-muted);
  font-size: 1.02rem;
  max-width: 72ch;
}

.hero-stats {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
}

.stat-chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: 10px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--text-muted);
  box-shadow: var(--shadow-xs);
}

.hero-cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 42px;
  padding: 10px 18px;
  border-radius: 12px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  font-size: 0.92rem;
  font-weight: 600;
  line-height: 1.25;
  cursor: pointer;
  transition: transform 0.14s ease, box-shadow 0.14s ease, background 0.14s ease, border-color 0.14s ease;
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
  border-color: var(--primary);
  text-decoration: none;
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), #4f46e5);
  color: #fff;
  border-color: transparent;
}
.btn-primary:hover {
  background: linear-gradient(135deg, var(--primary-hover), #4338ca);
  border-color: transparent;
}

.btn-accent {
  background: linear-gradient(135deg, var(--accent), #9333ea);
  color: #fff;
  border-color: transparent;
}
.btn-accent:hover {
  opacity: 0.94;
  border-color: transparent;
}

.btn-sm {
  min-height: 36px;
  padding: 7px 13px;
  font-size: 0.83rem;
  border-radius: 10px;
}

/* Section / Topic Cards */
.topic-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 26px 28px;
  box-shadow: var(--shadow-sm);
  transition: border-color 0.25s ease, box-shadow 0.25s ease;
  scroll-margin-top: 76px;
  min-width: 0;
}

.topic-card.is-playing {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 20%, transparent), var(--shadow-md);
}

.topic-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
  padding-bottom: 16px;
  margin-bottom: 18px;
  border-bottom: 1px solid var(--border);
}

.topic-badge {
  display: inline-flex;
  align-items: center;
  font-family: var(--font-display);
  font-size: 0.76rem;
  font-weight: 700;
  color: var(--primary-dark);
  background: var(--primary-soft);
  padding: 3px 11px;
  border-radius: 999px;
  margin-bottom: 8px;
}

.topic-header h2 {
  margin: 0;
  font-size: clamp(1.18rem, 2.2vw, 1.44rem);
  font-weight: 700;
  line-height: 1.3;
}

.topic-play-controls {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.playing-wave {
  display: none;
  align-items: flex-end;
  gap: 2px;
  height: 14px;
}
.topic-card.is-playing.audio-active .playing-wave {
  display: inline-flex;
}
.playing-wave span {
  width: 3px;
  background: currentColor;
  border-radius: 2px;
  animation: waveBar 0.8s infinite ease-in-out alternate;
}
.playing-wave span:nth-child(2) { animation-delay: 0.2s; }
.playing-wave span:nth-child(3) { animation-delay: 0.4s; }

@keyframes waveBar {
  from { height: 4px; }
  to { height: 14px; }
}

/* Pedagogical Callouts */
.story-box {
  background: var(--bg-story);
  border: 1px solid var(--border-story);
  border-left: 5px solid var(--warning);
  border-radius: 16px;
  padding: 16px 18px;
  margin: 14px 0 18px 0;
}

.story-title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.92rem;
  color: var(--warning);
  margin-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.concept-body h3 {
  margin: 20px 0 8px 0;
  font-size: 1.08rem;
  font-weight: 700;
}

.concept-body p {
  margin: 9px 0;
}

.concept-body ul, .concept-body ol {
  margin: 8px 0 14px 0;
  padding-left: 22px;
}

.concept-body li {
  margin-bottom: 7px;
}

.formula-box {
  background: var(--bg-formula);
  border: 1px solid var(--border);
  border-left: 4px solid var(--primary);
  border-radius: 14px;
  padding: 14px 16px;
  margin: 14px 0;
  font-family: var(--font-mono);
  font-size: 0.94rem;
  line-height: 1.65;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.example-box {
  background: var(--bg-soft);
  border: 1px solid color-mix(in srgb, var(--primary) 24%, var(--border));
  border-radius: 16px;
  padding: 15px 18px;
  margin: 14px 0;
}

.trap-box {
  background: var(--bg-trap);
  border: 1px solid var(--border-trap);
  border-left: 5px solid var(--danger);
  border-radius: 16px;
  padding: 14px 18px;
  margin: 16px 0;
}

.chem-table {
  width: 100%;
  border-collapse: collapse;
  margin: 14px 0;
  font-size: 0.9rem;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  display: block;
}
.chem-table th, .chem-table td {
  border: 1px solid var(--border);
  padding: 9px 12px;
  text-align: left;
  white-space: nowrap;
}
.chem-table th {
  background: var(--bg-soft);
  font-family: var(--font-display);
  font-weight: 700;
}

/* Interactive Animation Lab */
.lab-card {
  background: var(--bg-lab);
  border: 1px solid var(--border-lab);
  border-radius: 18px;
  padding: 18px;
  margin: 20px 0;
}

.lab-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}

.lab-title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1rem;
  color: var(--success);
  display: flex;
  align-items: center;
  gap: 8px;
}

.lab-stage {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 14px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.lab-stage canvas, .lab-stage svg {
  max-width: 100%;
  height: auto;
  display: block;
  border-radius: 10px;
  touch-action: pan-y;
}

.lab-stage canvas:not([style*="max-width"]), .lab-stage svg:not([style*="max-width"]) {
  width: 100%;
}

.lab-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px dashed var(--border-strong);
}

.lab-control {
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 150px;
  flex: 1 1 180px;
  font-size: 0.85rem;
  font-weight: 600;
}

.lab-control input[type="range"] {
  width: 100%;
  min-height: 28px;
  accent-color: var(--primary);
  cursor: pointer;
}

.lab-stage select, .lab-stage input[type="text"], .lab-stage input[type="number"] {
  max-width: 100%;
  min-height: 38px;
}

.lab-readout {
  margin-top: 10px;
  padding: 11px 14px;
  border-radius: 12px;
  background: var(--bg-soft);
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.55;
}

/* Transcript Accordion */
.transcript-box {
  margin-top: 16px;
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
}

.transcript-head {
  width: 100%;
  background: var(--bg-formula);
  border: none;
  padding: 12px 16px;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  text-align: left;
  font-weight: 600;
  font-size: 0.88rem;
  color: var(--text-muted);
  cursor: pointer;
}

.transcript-body {
  padding: 14px 16px;
  border-top: 1px solid var(--border);
  font-size: 0.94rem;
  display: none;
}

.transcript-body.open {
  display: block;
}

.transcript-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 10px;
  flex-wrap: wrap;
}

.t-tab.active {
  background: var(--primary);
  color: #fff;
  border-color: transparent;
}

/* Quiz Section */
.quiz-q {
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 18px;
  margin-bottom: 14px;
  background: var(--bg-formula);
}

.quiz-q-title {
  font-weight: 700;
  margin-bottom: 12px;
  line-height: 1.5;
}

.quiz-opts {
  display: grid;
  gap: 9px;
}

.quiz-opt {
  text-align: left;
  min-height: 44px;
  padding: 11px 14px;
  border-radius: 12px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  cursor: pointer;
  font-size: 0.92rem;
  line-height: 1.45;
  transition: border-color 0.15s ease, background 0.15s ease, transform 0.1s ease;
}

.quiz-opt:hover:not(:disabled) {
  border-color: var(--primary);
  background: var(--bg-soft);
}

.quiz-opt.correct {
  background: var(--success-soft);
  border-color: var(--success);
  font-weight: 600;
}

.quiz-opt.wrong {
  background: var(--bg-trap);
  border-color: var(--danger);
}

.quiz-explain {
  margin-top: 12px;
  padding: 12px 14px;
  border-radius: 12px;
  background: var(--bg-elevated);
  border-left: 4px solid var(--primary);
  font-size: 0.9rem;
  display: none;
}
.quiz-explain.show {
  display: block;
}

.quiz-scorebar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 18px;
  border-radius: 14px;
  background: var(--bg-soft);
  margin-bottom: 16px;
}

/* PYQ Section */
.pyq-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
}

.pyq-card {
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 16px 18px;
  margin-bottom: 12px;
  background: var(--bg-elevated);
}

.pyq-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  margin-bottom: 10px;
}

.pyq-tag {
  font-size: 0.75rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 999px;
  background: var(--bg-soft);
  color: var(--primary-dark);
}

.pyq-tag.marks {
  background: var(--accent-soft);
  color: var(--accent);
}

.pyq-answer {
  margin-top: 12px;
  padding: 14px 16px;
  border-radius: 12px;
  background: var(--bg-lab);
  border: 1px solid var(--border-lab);
  display: none;
}
.pyq-answer.show {
  display: block;
}

/* Sticky Audio Studio Dock */
.audio-dock {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 80;
  background: var(--bg-glass);
  backdrop-filter: blur(22px);
  -webkit-backdrop-filter: blur(22px);
  border-top: 1px solid var(--border-strong);
  box-shadow: 0 -10px 32px rgba(15, 23, 42, 0.14);
  padding: 10px 18px calc(10px + env(safe-area-inset-bottom, 0px)) 18px;
}

.audio-dock-inner {
  max-width: 1340px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(190px, 1.2fr) minmax(280px, 1.9fr) auto;
  gap: 14px;
  align-items: center;
}

.dock-now {
  min-width: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.dock-now-text {
  min-width: 0;
}

.dock-track-title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.89rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.dock-track-sub {
  font-size: 0.77rem;
  color: var(--text-subtle);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.dock-center {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.dock-buttons {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
}

.ctrl-btn {
  width: 36px;
  height: 36px;
  border-radius: 999px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  font-size: 0.88rem;
  font-weight: 700;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.12s ease, border-color 0.12s ease, background 0.12s ease;
}

.ctrl-btn:hover {
  transform: scale(1.06);
  border-color: var(--primary);
}

.ctrl-btn.play-main {
  width: 42px;
  height: 42px;
  background: linear-gradient(135deg, var(--primary), #4f46e5);
  color: #fff;
  border-color: transparent;
  font-size: 1.04rem;
  box-shadow: 0 4px 14px color-mix(in srgb, var(--primary) 40%, transparent);
}

.seek-row {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.74rem;
  font-variant-numeric: tabular-nums;
  color: var(--text-subtle);
}

.seek-row input[type="range"] {
  flex: 1;
  min-width: 0;
  height: 6px;
  accent-color: var(--primary);
  cursor: pointer;
}

.dock-options {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.seg-switch {
  display: inline-flex;
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  padding: 2px;
  background: var(--bg);
}

.seg-switch button {
  border: none;
  background: transparent;
  color: var(--text-muted);
  padding: 5px 11px;
  border-radius: 999px;
  font-size: 0.77rem;
  font-weight: 700;
  cursor: pointer;
}

.seg-switch button.active {
  background: linear-gradient(135deg, var(--primary), #4f46e5);
  color: #fff;
}

.toggle-chip {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 11px;
  border-radius: 999px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text-muted);
  font-size: 0.77rem;
  font-weight: 700;
  cursor: pointer;
}

.toggle-chip.on {
  background: var(--success-soft);
  color: var(--success);
  border-color: color-mix(in srgb, var(--success) 38%, transparent);
}

.speed-select {
  padding: 5px 9px;
  border-radius: 999px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  font-size: 0.77rem;
  font-weight: 700;
  cursor: pointer;
}

.dock-min-btn {
  display: none;
}

/* Portal Grid & Cards */
.portal-shell {
  max-width: 1220px;
  margin: 26px auto;
  padding: 0 20px;
}

.portal-filter-bar {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  align-items: center;
  margin-top: 12px;
}

.portal-search {
  flex: 1 1 240px;
  min-width: 0;
  min-height: 44px;
  padding: 11px 16px;
  border-radius: 12px;
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  font-size: 0.95rem;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(290px, 1fr));
  gap: 18px;
  margin-top: 18px;
}

.chapter-tile {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 20px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 14px;
  transition: transform 0.16s ease, box-shadow 0.16s ease, border-color 0.16s ease;
}

.chapter-tile:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--primary);
}

.chapter-tile h3 {
  margin: 0 0 6px 0;
  font-size: 1.1rem;
  line-height: 1.32;
}

/* =========================================================
   TABLET & MOBILE RESPONSIVE BREAKPOINTS
   ========================================================= */
@media (max-width: 980px) {
  .page-shell {
    grid-template-columns: 1fr;
    margin: 14px auto;
    padding: 0;
    gap: 14px;
  }

  .mobile-menu-btn {
    display: inline-flex;
  }

  .mobile-close-drawer {
    display: inline-flex;
  }

  .desktop-only-pill {
    display: none;
  }

  .drawer-backdrop {
    position: fixed;
    inset: 0;
    z-index: 90;
    background: rgba(2, 6, 23, 0.55);
    backdrop-filter: blur(4px);
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.22s ease;
    display: block;
  }
  .drawer-backdrop.open {
    opacity: 1;
    pointer-events: auto;
  }

  .sidebar {
    position: fixed !important;
    top: 0 !important;
    left: 0;
    bottom: 0;
    width: min(86vw, 330px);
    max-height: 100vh !important;
    z-index: 100;
    border-radius: 0 20px 20px 0;
    transform: translateX(-105%);
    transition: transform 0.25s cubic-bezier(0.22, 1, 0.36, 1);
    box-shadow: var(--shadow-lg);
    padding: 18px 16px 28px 16px;
  }
  .sidebar.open {
    transform: translateX(0);
  }
}

@media (max-width: 768px) {
  :root {
    --player-h: 112px;
  }

  body {
    font-size: 13.5px;
    line-height: 1.58;
  }

  .topbar-inner {
    padding: 8px 12px;
    gap: 8px;
  }

  .nav-pill {
    min-height: 34px;
    padding: 5px 10px;
    font-size: 0.78rem;
  }

  .portal-shell {
    margin: 14px auto;
    padding: 0 10px;
  }

  .hero-card {
    padding: 14px 12px;
    border-radius: 14px;
  }

  .hero-card h1 {
    font-size: 1.18rem;
    line-height: 1.28;
    margin: 8px 0 6px 0;
  }

  .hero-subtitle {
    font-size: 0.84rem;
    margin-bottom: 10px;
  }

  .hero-stats {
    gap: 5px;
    margin-bottom: 10px;
  }

  .stat-chip {
    padding: 4px 8px;
    font-size: 0.7rem;
    border-radius: 7px;
  }

  .hero-cta-row {
    flex-direction: column;
    align-items: stretch;
  }
  .hero-cta-row .btn {
    width: 100%;
  }

  .topic-card {
    padding: 13px 11px;
    border-radius: 14px;
    scroll-margin-top: 60px;
  }

  .topic-header h2 {
    font-size: 1.04rem;
    line-height: 1.3;
  }

  .topic-badge {
    font-size: 0.68rem;
    padding: 3px 8px;
  }

  .concept-body h3 {
    font-size: 0.96rem;
    margin-top: 12px;
  }

  .concept-body p, .concept-body li {
    font-size: 0.88rem;
  }

  .topic-header {
    padding-bottom: 12px;
    margin-bottom: 14px;
    gap: 10px;
  }

  .topic-play-controls {
    width: 100%;
  }
  .topic-play-controls .btn {
    flex: 1 1 0;
  }

  .story-box, .example-box, .trap-box, .lab-card {
    padding: 11px 11px;
    border-radius: 12px;
    font-size: 0.88rem;
  }

  .lab-title {
    font-size: 0.88rem;
  }

  .lab-stage {
    padding: 6px;
    border-radius: 10px;
  }

  .lab-controls {
    gap: 8px;
  }

  .lab-control {
    font-size: 0.78rem;
  }

  .lab-readout {
    font-size: 0.8rem;
    padding: 7px 10px;
  }

  .formula-box {
    padding: 9px 10px;
    font-size: 0.8rem;
  }

  .chem-table th, .chem-table td {
    padding: 6px 8px;
    font-size: 0.78rem;
  }

  .btn {
    font-size: 0.8rem;
    padding: 7px 11px;
  }

  .btn-sm {
    font-size: 0.75rem;
    padding: 5px 9px;
  }

  .quiz-q-title {
    font-size: 0.9rem;
  }

  .quiz-opt {
    font-size: 0.82rem;
    padding: 8px 10px;
  }

  .quiz-explain {
    font-size: 0.8rem;
  }

  .pyq-card {
    font-size: 0.86rem;
    padding: 11px 12px;
  }

  .pyq-tag {
    font-size: 0.68rem;
  }

  .transcript-head {
    font-size: 0.8rem;
  }

  .transcript-body {
    font-size: 0.84rem;
  }

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

  .chapter-tile {
    padding: 13px;
    border-radius: 14px;
  }

  .chapter-tile h3 {
    font-size: 0.98rem;
  }

  .chapter-tile p {
    font-size: 0.82rem;
  }

  /* Compact 2-row Mobile Audio Dock + Collapsible Mini Mode */
  .audio-dock {
    padding: 8px 12px calc(8px + env(safe-area-inset-bottom, 0px)) 12px;
  }

  .audio-dock-inner {
    grid-template-columns: 1fr;
    gap: 6px;
  }

  .dock-now {
    gap: 6px;
  }

  .dock-track-title {
    font-size: 0.82rem;
  }

  .dock-track-sub {
    display: none;
  }

  .dock-min-btn {
    display: inline-flex;
    flex-shrink: 0;
    height: 28px;
    padding: 0 9px;
    border-radius: 999px;
    border: 1px solid var(--border-strong);
    background: var(--bg-elevated);
    color: var(--text-muted);
    font-size: 0.72rem;
    font-weight: 700;
    align-items: center;
    cursor: pointer;
  }

  .dock-center {
    gap: 4px;
  }

  .dock-buttons {
    gap: 7px;
  }

  .ctrl-btn {
    width: 34px;
    height: 34px;
    font-size: 0.82rem;
  }

  .ctrl-btn.play-main {
    width: 38px;
    height: 38px;
    font-size: 0.96rem;
  }

  .dock-options {
    justify-content: space-between;
    gap: 6px;
  }

  .seg-switch button {
    padding: 4px 9px;
    font-size: 0.72rem;
  }

  .toggle-chip, .speed-select {
    padding: 4px 9px;
    font-size: 0.72rem;
  }

  .audio-dock.minimized .dock-center .seek-row,
  .audio-dock.minimized .dock-options {
    display: none;
  }

  .audio-dock.minimized .audio-dock-inner {
    grid-template-columns: 1fr auto;
    align-items: center;
    gap: 8px;
  }

  .audio-dock.minimized .dock-buttons .ctrl-btn:not(.play-main):not(#btn-next-track) {
    display: none;
  }
}