/* ==========================================================================
   LibNext Digital Library — Mathematics Learning Portal
   Stylesheet
   --------------------------------------------------------------------------
   Sections:
   1.  CSS Reset & Base
   2.  Theme Variables (Dark / Light)
   3.  Typography & Utility Classes
   4.  Loading Screen & Skeletons
   5.  Layout: Header / Nav / Breadcrumb
   6.  Search Bar
   7.  Hero / Section Headings
   8.  Card Grids (Classes, Subjects, Chapters)
   9.  Horizontal Rails (Continue Watching, Recently Added, Bookmarks)
   10. Video Playlist List
   11. Custom Video Player
   12. Buttons, Badges, Toggles, Empty States
   13. Footer
   14. Toast Notifications
   15. TV / Smartboard Mode
   16. Responsive Breakpoints
   17. Animations
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. CSS RESET & BASE
   -------------------------------------------------------------------------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

img, video {
  max-width: 100%;
  display: block;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  color: inherit;
}

a {
  color: inherit;
  text-decoration: none;
}

ul, ol {
  list-style: none;
}

input {
  font-family: inherit;
}

/* --------------------------------------------------------------------------
   2. THEME VARIABLES
   -------------------------------------------------------------------------- */
:root {
  /* Brand accent gradient */
  --accent-1: #6366f1;
  --accent-2: #8b5cf6;
  --accent-3: #06b6d4;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;

  /* Radii & spacing */
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;
  --radius-pill: 999px;

  --gap-xs: 6px;
  --gap-sm: 12px;
  --gap-md: 20px;
  --gap-lg: 32px;
  --gap-xl: 48px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(.4,0,.2,1);
  --transition-base: 250ms cubic-bezier(.4,0,.2,1);
  --transition-slow: 450ms cubic-bezier(.4,0,.2,1);

  /* Layout */
  --header-h: 72px;
  --max-width: 1600px;

  /* Focus ring (used heavily for TV/remote navigation) */
  --focus-ring: 0 0 0 3px rgba(255,255,255,0.9), 0 0 0 7px var(--accent-1), 0 8px 24px rgba(99,102,241,.55);
}

/* ---- Dark theme (default) ---- */
:root,
[data-theme="dark"] {
  --bg-0: #06070d;
  --bg-1: #0b0e1a;
  --bg-2: #11152a;
  --bg-elevated: #161b33;
  --glass-bg: rgba(255, 255, 255, 0.05);
  --glass-bg-strong: rgba(255, 255, 255, 0.09);
  --glass-border: rgba(255, 255, 255, 0.10);
  --text-primary: #f5f6fb;
  --text-secondary: #b6bbd4;
  --text-muted: #7d83a3;
  --shadow-card: 0 10px 30px rgba(0, 0, 0, 0.45);
  --shadow-elevated: 0 20px 60px rgba(0, 0, 0, 0.6);
  --gradient-bg: radial-gradient(1200px 800px at 10% -10%, rgba(99,102,241,.25), transparent 60%),
                  radial-gradient(1000px 700px at 100% 0%, rgba(6,182,212,.18), transparent 55%),
                  radial-gradient(1200px 900px at 50% 120%, rgba(139,92,246,.18), transparent 60%),
                  var(--bg-0);
  --skeleton-base: rgba(255,255,255,0.06);
  --skeleton-shine: rgba(255,255,255,0.14);
  --player-bg: #000;
  --scrollbar-thumb: rgba(255,255,255,.18);
}

/* ---- Light theme ---- */
[data-theme="light"] {
  --bg-0: #eef0fb;
  --bg-1: #f7f8fd;
  --bg-2: #ffffff;
  --bg-elevated: #ffffff;
  --glass-bg: rgba(255, 255, 255, 0.65);
  --glass-bg-strong: rgba(255, 255, 255, 0.85);
  --glass-border: rgba(15, 23, 42, 0.08);
  --text-primary: #161a2e;
  --text-secondary: #4b5170;
  --text-muted: #8189ab;
  --shadow-card: 0 10px 30px rgba(80, 90, 160, 0.12);
  --shadow-elevated: 0 20px 50px rgba(80, 90, 160, 0.18);
  --gradient-bg: radial-gradient(1200px 800px at 10% -10%, rgba(99,102,241,.14), transparent 60%),
                  radial-gradient(1000px 700px at 100% 0%, rgba(6,182,212,.12), transparent 55%),
                  radial-gradient(1200px 900px at 50% 120%, rgba(139,92,246,.12), transparent 60%),
                  var(--bg-0);
  --skeleton-base: rgba(15,23,42,0.06);
  --skeleton-shine: rgba(15,23,42,0.12);
  --player-bg: #0a0a0a;
  --scrollbar-thumb: rgba(15,23,42,.18);
}

/* --------------------------------------------------------------------------
   3. TYPOGRAPHY & UTILITIES
   -------------------------------------------------------------------------- */
body {
  font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
  background: var(--gradient-bg);
  background-attachment: fixed;
  color: var(--text-primary);
  line-height: 1.5;
  min-height: 100vh;
  transition: background var(--transition-slow), color var(--transition-base);
  overflow-x: hidden;
}

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

.hidden { display: none !important; }

.gradient-text {
  background: linear-gradient(135deg, var(--accent-1), var(--accent-3));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 clamp(16px, 4vw, 48px);
}

::selection {
  background: var(--accent-1);
  color: #fff;
}

/* Scrollbars */
* { scrollbar-width: thin; scrollbar-color: var(--scrollbar-thumb) transparent; }
*::-webkit-scrollbar { height: 8px; width: 8px; }
*::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: var(--radius-pill); }
*::-webkit-scrollbar-track { background: transparent; }

/* Focus visibility everywhere (a11y + TV remote) */
a:focus-visible,
button:focus-visible,
[tabindex]:focus-visible,
input:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
  z-index: 2;
}

/* --------------------------------------------------------------------------
   4. LOADING SCREEN & SKELETONS
   -------------------------------------------------------------------------- */
#app-loader {
  position: fixed;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--gap-md);
  background: var(--bg-0);
  background: var(--gradient-bg);
  z-index: 9999;
  transition: opacity var(--transition-slow), visibility var(--transition-slow);
}
#app-loader.fade-out {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}
.loader-logo {
  font-size: 2.4rem;
  font-weight: 800;
  letter-spacing: -1px;
}
.loader-bar {
  width: 220px;
  height: 4px;
  border-radius: var(--radius-pill);
  background: var(--glass-bg);
  overflow: hidden;
}
.loader-bar::after {
  content: '';
  display: block;
  width: 40%;
  height: 100%;
  background: linear-gradient(90deg, var(--accent-1), var(--accent-3));
  border-radius: var(--radius-pill);
  animation: loaderSlide 1.1s ease-in-out infinite;
}
.loader-text { color: var(--text-muted); font-size: .9rem; letter-spacing: .5px; }

/* Skeleton shimmer */
.skeleton {
  position: relative;
  overflow: hidden;
  background: var(--skeleton-base);
  border-radius: var(--radius-md);
}
.skeleton::after {
  content: '';
  position: absolute;
  inset: 0;
  transform: translateX(-100%);
  background: linear-gradient(90deg, transparent, var(--skeleton-shine), transparent);
  animation: shimmer 1.5s infinite;
}
.skeleton-card { aspect-ratio: 16/10; width: 100%; }
.skeleton-line { height: 14px; border-radius: 6px; margin-top: 10px; }
.skeleton-line.w-60 { width: 60%; }
.skeleton-line.w-40 { width: 40%; }

/* --------------------------------------------------------------------------
   5. LAYOUT: HEADER / NAV / BREADCRUMB
   -------------------------------------------------------------------------- */
#site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  display: flex;
  align-items: center;
  backdrop-filter: blur(18px) saturate(160%);
  -webkit-backdrop-filter: blur(18px) saturate(160%);
  background: var(--glass-bg);
  border-bottom: 1px solid var(--glass-border);
  transition: background var(--transition-base);
}
.header-inner {
  display: flex;
  align-items: center;
  gap: var(--gap-md);
  width: 100%;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.25rem;
  letter-spacing: -.5px;
  flex-shrink: 0;
}
.brand-mark {
  display: grid;
  place-items: center;
  width: 38px; height: 38px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--accent-1), var(--accent-3));
  color: #fff;
  font-size: 1.1rem;
  box-shadow: 0 6px 18px rgba(99,102,241,.45);
}
.brand-sub {
  font-size: .65rem;
  font-weight: 600;
  letter-spacing: 2px;
  color: var(--text-muted);
  text-transform: uppercase;
  display: block;
  margin-top: -2px;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--gap-sm);
  margin-left: auto;
  flex-shrink: 0;
}

.icon-btn {
  display: grid;
  place-items: center;
  width: 42px; height: 42px;
  border-radius: var(--radius-pill);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  color: var(--text-primary);
  transition: transform var(--transition-fast), background var(--transition-fast), color var(--transition-fast);
  position: relative;
}
.icon-btn:hover { background: var(--glass-bg-strong); transform: translateY(-2px); }
.icon-btn:active { transform: translateY(0) scale(.96); }
.icon-btn svg { width: 20px; height: 20px; }
.icon-btn.active { color: var(--accent-1); border-color: var(--accent-1); }

#theme-toggle .icon-moon { display: none; }
[data-theme="light"] #theme-toggle .icon-sun { display: none; }
[data-theme="light"] #theme-toggle .icon-moon { display: block; }

/* Breadcrumb */
#breadcrumb-bar {
  display: flex;
  align-items: center;
  gap: var(--gap-sm);
  padding: 14px clamp(16px, 4vw, 48px);
  max-width: var(--max-width);
  margin: 0 auto;
  width: 100%;
  font-size: .92rem;
  color: var(--text-secondary);
  flex-wrap: wrap;
}
#breadcrumb-bar.hidden { display: none; }
.crumb {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: var(--radius-pill);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  transition: all var(--transition-fast);
  font-weight: 600;
}
.crumb:hover, .crumb:focus-visible { background: var(--glass-bg-strong); color: var(--text-primary); }
.crumb.current {
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  color: #fff;
  border-color: transparent;
}
.crumb-sep { color: var(--text-muted); font-size: .8rem; }

/* --------------------------------------------------------------------------
   6. SEARCH BAR
   -------------------------------------------------------------------------- */
.search-wrap {
  flex: 1 1 420px;
  max-width: 520px;
  position: relative;
}
.search-wrap svg {
  position: absolute;
  left: 16px; top: 50%;
  transform: translateY(-50%);
  width: 18px; height: 18px;
  color: var(--text-muted);
  pointer-events: none;
}
#search-input {
  width: 100%;
  height: 44px;
  padding: 0 42px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--glass-border);
  background: var(--glass-bg);
  color: var(--text-primary);
  font-size: .95rem;
  transition: all var(--transition-fast);
}
#search-input::placeholder { color: var(--text-muted); }
#search-input:focus {
  background: var(--glass-bg-strong);
  border-color: var(--accent-1);
  box-shadow: 0 0 0 4px rgba(99,102,241,.18);
  outline: none;
}
.search-clear {
  position: absolute;
  right: 8px; top: 50%;
  transform: translateY(-50%);
  width: 28px; height: 28px;
  border-radius: 50%;
  display: none;
  place-items: center;
  background: var(--glass-bg-strong);
  color: var(--text-secondary);
}
.search-clear svg { width: 14px; height: 14px; }
.search-wrap.has-value .search-clear { display: grid; }

/* Search results panel */
#search-results {
  position: absolute;
  top: calc(100% + 10px);
  left: 0; right: 0;
  max-height: 70vh;
  overflow-y: auto;
  background: var(--bg-elevated);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-elevated);
  z-index: 200;
  padding: 8px;
}
#search-results.hidden { display: none; }
.search-result-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  transition: background var(--transition-fast);
  cursor: pointer;
  width: 100%;
  text-align: left;
}
.search-result-item:hover, .search-result-item:focus-visible { background: var(--glass-bg); }
.search-result-thumb {
  flex-shrink: 0;
  width: 64px; height: 40px;
  border-radius: 6px;
  display: grid;
  place-items: center;
  font-size: 1.1rem;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-3));
  color: #fff;
}
.search-result-meta { display: flex; flex-direction: column; gap: 2px; min-width: 0; }
.search-result-title {
  font-weight: 600;
  font-size: .9rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.search-result-sub { font-size: .75rem; color: var(--text-muted); }
.search-empty {
  padding: 24px;
  text-align: center;
  color: var(--text-muted);
  font-size: .9rem;
}

/* --------------------------------------------------------------------------
   7. HERO / SECTION HEADINGS
   -------------------------------------------------------------------------- */
main { display: block; min-height: 60vh; padding-bottom: var(--gap-xl); }

.view { animation: fadeSlideUp var(--transition-slow) both; }
.view.hidden { display: none; }

.hero {
  padding: clamp(28px, 6vw, 64px) 0 clamp(16px, 3vw, 32px);
  text-align: center;
}
.hero h1 {
  font-size: clamp(1.8rem, 5vw, 3.2rem);
  font-weight: 800;
  letter-spacing: -1.5px;
  margin-bottom: 10px;
}
.hero p {
  color: var(--text-secondary);
  font-size: clamp(.95rem, 2vw, 1.15rem);
  max-width: 640px;
  margin: 0 auto;
}

.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--gap-md);
  margin: var(--gap-lg) 0 var(--gap-md);
}
.section-head h2 {
  font-size: clamp(1.1rem, 2.4vw, 1.5rem);
  font-weight: 800;
  letter-spacing: -.5px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.section-head .section-count {
  font-size: .8rem;
  font-weight: 600;
  color: var(--text-muted);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  padding: 3px 10px;
  border-radius: var(--radius-pill);
}
.section-head-action {
  font-size: .85rem;
  font-weight: 700;
  color: var(--accent-1);
  padding: 6px 4px;
  border-radius: var(--radius-sm);
}
.section-head-action:hover { text-decoration: underline; }

/* --------------------------------------------------------------------------
   8. CARD GRIDS
   -------------------------------------------------------------------------- */
.grid {
  display: grid;
  gap: var(--gap-md);
}
.grid-classes {
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: var(--gap-sm);
}
.grid-subjects {
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
}
.grid-chapters {
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
}

/* Class card */
.class-card {
  position: relative;
  aspect-ratio: 1 / 1;
  border-radius: var(--radius-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 6px;
  cursor: pointer;
  overflow: hidden;
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
  text-align: center;
  padding: 10px;
}
.class-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-3));
  opacity: 0;
  transition: opacity var(--transition-base);
}
.class-card:hover, .class-card:focus-visible {
  transform: translateY(-6px) scale(1.03);
  box-shadow: var(--shadow-elevated);
  border-color: transparent;
}
.class-card:hover::before, .class-card:focus-visible::before { opacity: 1; }
.class-card .class-num {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 800;
  position: relative;
  z-index: 1;
  transition: color var(--transition-base);
}
.class-card .class-label {
  font-size: .8rem;
  color: var(--text-muted);
  font-weight: 600;
  position: relative;
  z-index: 1;
  transition: color var(--transition-base);
}
.class-card:hover .class-num, .class-card:hover .class-label,
.class-card:focus-visible .class-num, .class-card:focus-visible .class-label { color: #fff; }
.class-card .class-badge {
  position: absolute;
  top: 10px; right: 10px;
  font-size: .62rem;
  font-weight: 700;
  letter-spacing: .5px;
  text-transform: uppercase;
  padding: 4px 8px;
  border-radius: var(--radius-pill);
  background: var(--success);
  color: #fff;
  z-index: 2;
}

/* Subject card */
.subject-card {
  position: relative;
  border-radius: var(--radius-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  padding: var(--gap-lg) var(--gap-md);
  display: flex;
  flex-direction: column;
  gap: 10px;
  cursor: pointer;
  overflow: hidden;
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
  min-height: 170px;
  justify-content: flex-end;
}
.subject-card:hover, .subject-card:focus-visible {
  transform: translateY(-6px);
  box-shadow: var(--shadow-elevated);
  border-color: var(--card-accent, var(--accent-1));
}
.subject-card .subject-icon {
  position: absolute;
  top: 18px; left: 18px;
  width: 52px; height: 52px;
  border-radius: var(--radius-md);
  display: grid;
  place-items: center;
  background: linear-gradient(135deg, var(--card-accent, var(--accent-1)), var(--accent-3));
  color: #fff;
  font-size: 1.5rem;
  box-shadow: 0 8px 24px rgba(0,0,0,.25);
}
.subject-card .subject-icon svg { width: 26px; height: 26px; }
.subject-card h3 { font-size: 1.15rem; font-weight: 800; letter-spacing: -.3px; }
.subject-card .subject-meta { font-size: .8rem; color: var(--text-muted); }
.subject-card .subject-glow {
  position: absolute;
  width: 160px; height: 160px;
  border-radius: 50%;
  background: var(--card-accent, var(--accent-1));
  filter: blur(60px);
  opacity: .25;
  top: -40px; right: -40px;
  transition: opacity var(--transition-base);
}
.subject-card:hover .subject-glow { opacity: .4; }
.subject-card.coming-soon {
  cursor: default;
  opacity: .6;
}
.subject-card.coming-soon:hover { transform: none; box-shadow: var(--shadow-card); border-color: var(--glass-border); }
.subject-card .badge {
  position: absolute;
  top: 18px; right: 18px;
  font-size: .62rem;
  font-weight: 700;
  letter-spacing: .5px;
  text-transform: uppercase;
  padding: 4px 10px;
  border-radius: var(--radius-pill);
}
.subject-card .badge.available { background: var(--success); color: #fff; }
.subject-card .badge.soon { background: var(--glass-bg-strong); color: var(--text-muted); border: 1px solid var(--glass-border); }

/* Chapter card */
.chapter-card {
  position: relative;
  border-radius: var(--radius-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  padding: var(--gap-md);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: 10px;
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
}
.chapter-card:hover, .chapter-card:focus-visible {
  transform: translateY(-4px);
  box-shadow: var(--shadow-elevated);
  border-color: var(--accent-1);
}
.chapter-card .chapter-index {
  font-size: .72rem;
  font-weight: 800;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--accent-1);
}
.chapter-card h3 { font-size: 1.05rem; font-weight: 700; line-height: 1.35; }
.chapter-card .chapter-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: .8rem;
  color: var(--text-muted);
  margin-top: auto;
}
.chapter-progress-track {
  height: 6px;
  border-radius: var(--radius-pill);
  background: var(--glass-bg-strong);
  overflow: hidden;
}
.chapter-progress-fill {
  height: 100%;
  border-radius: var(--radius-pill);
  background: linear-gradient(90deg, var(--accent-1), var(--accent-3));
  width: 0%;
  transition: width var(--transition-slow);
}

/* --------------------------------------------------------------------------
   9. HORIZONTAL RAILS (Continue Watching / Recently Added / Bookmarks)
   -------------------------------------------------------------------------- */
.rail {
  display: flex;
  gap: var(--gap-md);
  overflow-x: auto;
  padding-bottom: 14px;
  scroll-snap-type: x proximate;
}
.rail::-webkit-scrollbar { height: 6px; }

.rail-card {
  flex: 0 0 auto;
  width: 260px;
  scroll-snap-align: start;
  border-radius: var(--radius-md);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  overflow: hidden;
  cursor: pointer;
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
}
.rail-card:hover, .rail-card:focus-visible {
  transform: translateY(-5px) scale(1.02);
  box-shadow: var(--shadow-elevated);
  border-color: var(--accent-1);
}
.rail-thumb {
  position: relative;
  aspect-ratio: 16/9;
  display: grid;
  place-items: center;
  font-size: 2rem;
  color: #fff;
  overflow: hidden;
}
.rail-thumb .thumb-play {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  background: rgba(0,0,0,.25);
  opacity: 0;
  transition: opacity var(--transition-fast);
}
.rail-card:hover .thumb-play, .rail-card:focus-visible .thumb-play { opacity: 1; }
.thumb-play svg { width: 40px; height: 40px; filter: drop-shadow(0 4px 10px rgba(0,0,0,.4)); }
.rail-thumb .thumb-progress {
  position: absolute;
  bottom: 0; left: 0; right: 0;
  height: 4px;
  background: rgba(255,255,255,.25);
}
.rail-thumb .thumb-progress span {
  display: block;
  height: 100%;
  background: var(--accent-3);
}
.rail-thumb .thumb-bookmark {
  position: absolute;
  top: 8px; right: 8px;
  width: 30px; height: 30px;
  border-radius: 50%;
  background: rgba(0,0,0,.45);
  display: grid;
  place-items: center;
  color: #fff;
  z-index: 2;
}
.rail-thumb .thumb-bookmark.active { color: var(--warning); }
.rail-thumb .thumb-bookmark svg { width: 16px; height: 16px; }
.rail-thumb .thumb-new {
  position: absolute;
  top: 8px; left: 8px;
  font-size: .6rem;
  font-weight: 800;
  letter-spacing: 1px;
  text-transform: uppercase;
  padding: 3px 8px;
  border-radius: var(--radius-pill);
  background: var(--accent-2);
  color: #fff;
}
.rail-body { padding: 12px 14px 14px; }
.rail-title {
  font-size: .9rem;
  font-weight: 700;
  line-height: 1.35;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.rail-sub {
  font-size: .75rem;
  color: var(--text-muted);
  margin-top: 4px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Thumbnail color variety based on chapter index */
.thumb-1 { background: linear-gradient(135deg, #6366f1, #06b6d4); }
.thumb-2 { background: linear-gradient(135deg, #8b5cf6, #ec4899); }
.thumb-3 { background: linear-gradient(135deg, #10b981, #06b6d4); }
.thumb-4 { background: linear-gradient(135deg, #f59e0b, #ef4444); }
.thumb-5 { background: linear-gradient(135deg, #06b6d4, #6366f1); }
.thumb-6 { background: linear-gradient(135deg, #ec4899, #8b5cf6); }

/* --------------------------------------------------------------------------
   10. VIDEO PLAYLIST LIST
   -------------------------------------------------------------------------- */
.playlist {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.playlist-item {
  display: flex;
  align-items: center;
  gap: var(--gap-sm);
  padding: 10px 12px;
  border-radius: var(--radius-md);
  background: var(--glass-bg);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background var(--transition-fast), border-color var(--transition-fast), transform var(--transition-fast);
  text-align: left;
  width: 100%;
}
.playlist-item:hover, .playlist-item:focus-visible {
  background: var(--glass-bg-strong);
  border-color: var(--accent-1);
}
.playlist-item.active {
  background: linear-gradient(90deg, rgba(99,102,241,.18), rgba(6,182,212,.10));
  border-color: var(--accent-1);
}
.playlist-thumb {
  flex-shrink: 0;
  width: 92px; height: 56px;
  border-radius: 8px;
  display: grid;
  place-items: center;
  color: #fff;
  font-weight: 800;
  font-size: 1rem;
  position: relative;
  overflow: hidden;
}
.playlist-thumb .pl-progress {
  position: absolute; bottom: 0; left: 0; right: 0; height: 3px;
  background: rgba(255,255,255,.25);
}
.playlist-thumb .pl-progress span { display: block; height: 100%; background: var(--accent-3); }
.playlist-thumb .pl-playing {
  position: absolute; inset: 0;
  display: grid; place-items: center;
  background: rgba(0,0,0,.35);
}
.playlist-thumb .pl-playing svg { width: 22px; height: 22px; }
.playlist-meta { flex: 1; min-width: 0; }
.playlist-title {
  font-size: .9rem;
  font-weight: 600;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  line-height: 1.35;
}
.playlist-sub { font-size: .75rem; color: var(--text-muted); margin-top: 3px; }
.playlist-actions { display: flex; align-items: center; gap: 6px; flex-shrink: 0; }
.playlist-check {
  width: 22px; height: 22px;
  border-radius: 50%;
  display: grid; place-items: center;
  background: var(--success);
  color: #fff;
  flex-shrink: 0;
}
.playlist-check svg { width: 13px; height: 13px; }
.playlist-check.hidden { display: none; }

/* --------------------------------------------------------------------------
   11. CUSTOM VIDEO PLAYER
   -------------------------------------------------------------------------- */
.player-layout {
  display: grid;
  grid-template-columns: minmax(0, 2.4fr) minmax(280px, 1fr);
  gap: var(--gap-lg);
  align-items: start;
}
.player-main { display: flex; flex-direction: column; gap: var(--gap-md); }

.player-shell {
  position: relative;
  width: 100%;
  background: var(--player-bg);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-elevated);
  aspect-ratio: 16 / 9;
}
.player-shell video {
  width: 100%; height: 100%;
  object-fit: contain;
  background: #000;
}
.player-shell:fullscreen, .player-shell:-webkit-full-screen {
  border-radius: 0;
}
.player-overlay-center {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  pointer-events: none;
}
.player-big-play {
  width: 84px; height: 84px;
  border-radius: 50%;
  background: rgba(255,255,255,.14);
  backdrop-filter: blur(6px);
  display: grid; place-items: center;
  color: #fff;
  opacity: 0;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
  pointer-events: auto;
}
.player-big-play svg { width: 36px; height: 36px; }
.player-shell.paused .player-big-play,
.player-shell:hover .player-big-play { opacity: 1; }
.player-big-play:hover { transform: scale(1.08); }

.player-spinner {
  width: 48px; height: 48px;
  border: 4px solid rgba(255,255,255,.2);
  border-top-color: var(--accent-3);
  border-radius: 50%;
  animation: spin .8s linear infinite;
  opacity: 0;
  pointer-events: none;
}
.player-shell.buffering .player-spinner { opacity: 1; }

/* Controls bar */
.player-controls {
  position: absolute;
  left: 0; right: 0; bottom: 0;
  padding: 28px 16px 12px;
  background: linear-gradient(180deg, transparent, rgba(0,0,0,.78));
  display: flex;
  flex-direction: column;
  gap: 8px;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity var(--transition-base), transform var(--transition-base);
  color: #fff;
}
.player-shell.show-controls .player-controls,
.player-shell.paused .player-controls { opacity: 1; transform: translateY(0); }

.progress-row { display: flex; align-items: center; gap: 10px; }
.player-time { font-size: .75rem; font-variant-numeric: tabular-nums; min-width: 42px; text-align: center; }

.seek-bar {
  position: relative;
  flex: 1;
  height: 14px;
  display: flex;
  align-items: center;
  cursor: pointer;
}
.seek-track {
  width: 100%; height: 4px;
  border-radius: var(--radius-pill);
  background: rgba(255,255,255,.25);
  position: relative;
  overflow: hidden;
}
.seek-buffered {
  position: absolute; left: 0; top: 0; bottom: 0;
  background: rgba(255,255,255,.35);
  width: 0%;
}
.seek-filled {
  position: absolute; left: 0; top: 0; bottom: 0;
  background: linear-gradient(90deg, var(--accent-1), var(--accent-3));
  width: 0%;
}
.seek-handle {
  position: absolute;
  top: 50%; left: 0%;
  width: 13px; height: 13px;
  border-radius: 50%;
  background: #fff;
  transform: translate(-50%, -50%) scale(0);
  transition: transform var(--transition-fast);
  box-shadow: 0 2px 6px rgba(0,0,0,.4);
}
.seek-bar:hover .seek-handle, .seek-bar:focus-visible .seek-handle { transform: translate(-50%, -50%) scale(1); }
.seek-bar:focus-visible { outline: none; }
.seek-bar:focus-visible .seek-track { box-shadow: 0 0 0 3px var(--accent-1); }

.controls-row {
  display: flex;
  align-items: center;
  gap: 6px;
}
.controls-row .spacer { flex: 1; }
.ctrl-btn {
  display: grid; place-items: center;
  width: 38px; height: 38px;
  border-radius: 50%;
  color: #fff;
  transition: background var(--transition-fast), transform var(--transition-fast);
}
.ctrl-btn:hover { background: rgba(255,255,255,.15); }
.ctrl-btn:active { transform: scale(.92); }
.ctrl-btn svg { width: 20px; height: 20px; }
.ctrl-btn.play-pause svg { width: 24px; height: 24px; }

.volume-group { display: flex; align-items: center; gap: 6px; }
.volume-slider {
  width: 0;
  overflow: hidden;
  transition: width var(--transition-base);
}
.volume-group:hover .volume-slider, .volume-group:focus-within .volume-slider { width: 80px; }
.volume-slider input[type="range"] { width: 80px; }

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  height: 4px;
  background: rgba(255,255,255,.25);
  border-radius: var(--radius-pill);
  outline: none;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 12px; height: 12px;
  border-radius: 50%;
  background: #fff;
  cursor: pointer;
}
input[type="range"]::-moz-range-thumb {
  width: 12px; height: 12px;
  border: none;
  border-radius: 50%;
  background: #fff;
  cursor: pointer;
}

.rate-btn {
  font-size: .78rem;
  font-weight: 700;
  padding: 0 8px;
  height: 32px;
  border-radius: var(--radius-pill);
  color: #fff;
  background: rgba(255,255,255,.12);
  white-space: nowrap;
}
.rate-btn:hover { background: rgba(255,255,255,.22); }

/* Now playing info below player */
.now-playing {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--gap-md);
  flex-wrap: wrap;
}
.now-playing h2 { font-size: clamp(1.1rem, 2.4vw, 1.55rem); font-weight: 800; letter-spacing: -.3px; }
.now-playing .np-chapter { color: var(--text-muted); font-size: .85rem; margin-top: 4px; }
.now-playing-actions { display: flex; gap: 8px; flex-shrink: 0; }

.video-progress-bar {
  height: 6px;
  border-radius: var(--radius-pill);
  background: var(--glass-bg-strong);
  overflow: hidden;
}
.video-progress-bar span {
  display: block; height: 100%;
  background: linear-gradient(90deg, var(--accent-1), var(--accent-3));
  width: 0%;
  transition: width .3s linear;
}

/* Player sidebar */
.player-sidebar {
  display: flex;
  flex-direction: column;
  gap: var(--gap-md);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: var(--gap-md);
  max-height: calc(100vh - var(--header-h) - 40px);
  position: sticky;
  top: calc(var(--header-h) + 20px);
  overflow-y: auto;
}
.player-sidebar h3 {
  font-size: 1rem;
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* --------------------------------------------------------------------------
   12. BUTTONS, BADGES, TOGGLES, EMPTY STATES
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: var(--radius-pill);
  font-weight: 700;
  font-size: .88rem;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast);
  border: 1px solid var(--glass-border);
  background: var(--glass-bg);
  color: var(--text-primary);
}
.btn svg { width: 16px; height: 16px; }
.btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-card); }
.btn-primary {
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  color: #fff;
  border-color: transparent;
}
.btn-ghost { background: transparent; }
.btn.active { color: var(--warning); border-color: var(--warning); }

.empty-state {
  text-align: center;
  padding: var(--gap-xl) var(--gap-md);
  color: var(--text-muted);
}
.empty-state .empty-icon { font-size: 2.6rem; margin-bottom: 10px; }
.empty-state h3 { color: var(--text-primary); font-size: 1.1rem; margin-bottom: 6px; }
.empty-state p { font-size: .9rem; max-width: 420px; margin: 0 auto; }

/* --------------------------------------------------------------------------
   13. FOOTER
   -------------------------------------------------------------------------- */
#site-footer {
  border-top: 1px solid var(--glass-border);
  padding: var(--gap-lg) 0;
  margin-top: var(--gap-xl);
  text-align: center;
  color: var(--text-muted);
  font-size: .85rem;
}
#site-footer .footer-links {
  display: flex; gap: var(--gap-md); justify-content: center; margin-top: 8px; flex-wrap: wrap;
}
#site-footer .footer-links span { font-weight: 600; color: var(--text-secondary); }

/* --------------------------------------------------------------------------
   14. TOAST NOTIFICATIONS
   -------------------------------------------------------------------------- */
#toast-container {
  position: fixed;
  bottom: 24px; left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  gap: 10px;
  z-index: 1000;
  width: min(92vw, 380px);
  align-items: center;
}
.toast {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 18px;
  border-radius: var(--radius-pill);
  background: var(--bg-elevated);
  border: 1px solid var(--glass-border);
  box-shadow: var(--shadow-elevated);
  font-size: .88rem;
  font-weight: 600;
  animation: toastIn .35s ease both;
}
.toast.leaving { animation: toastOut .3s ease both; }
.toast svg { width: 18px; height: 18px; color: var(--success); flex-shrink: 0; }

/* --------------------------------------------------------------------------
   15. TV / SMARTBOARD MODE
   -------------------------------------------------------------------------- */
body.tv-mode {
  font-size: 1.18em;
}
body.tv-mode .container { padding: 0 clamp(24px, 5vw, 80px); }
body.tv-mode .grid-classes { grid-template-columns: repeat(auto-fill, minmax(190px, 1fr)); gap: var(--gap-md); }
body.tv-mode .grid-subjects { grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }
body.tv-mode .grid-chapters { grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); }
body.tv-mode .rail-card { width: 320px; }
body.tv-mode .icon-btn { width: 52px; height: 52px; }
body.tv-mode .icon-btn svg { width: 24px; height: 24px; }
body.tv-mode #search-input { height: 54px; font-size: 1.05rem; }
body.tv-mode .btn { padding: 14px 24px; font-size: 1rem; }

/* Stronger, more visible focus ring for remote/keyboard nav */
body.tv-mode :focus-visible,
body.tv-mode .tv-focus {
  outline: none;
  box-shadow: 0 0 0 4px rgba(255,255,255,1), 0 0 0 9px var(--accent-1), 0 10px 30px rgba(99,102,241,.6) !important;
  transform: translateY(-4px) scale(1.02);
  z-index: 5;
  position: relative;
}
body.tv-mode .player-controls { padding-bottom: 24px; }
body.tv-mode .ctrl-btn { width: 50px; height: 50px; }
body.tv-mode .ctrl-btn svg { width: 26px; height: 26px; }
body.tv-mode .ctrl-btn.play-pause svg { width: 32px; height: 32px; }

/* --------------------------------------------------------------------------
   16. RESPONSIVE BREAKPOINTS
   -------------------------------------------------------------------------- */
@media (max-width: 1100px) {
  .player-layout { grid-template-columns: 1fr; }
  .player-sidebar { position: static; max-height: none; }
}

@media (max-width: 860px) {
  :root { --header-h: 64px; }
  .header-inner { flex-wrap: wrap; }
  .search-wrap { order: 3; flex-basis: 100%; max-width: none; }
  .brand-sub { display: none; }
  .grid-classes { grid-template-columns: repeat(auto-fill, minmax(110px, 1fr)); }
  .rail-card { width: 210px; }
}

@media (max-width: 560px) {
  .grid-classes { grid-template-columns: repeat(4, 1fr); gap: 8px; }
  .grid-subjects, .grid-chapters { grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); }
  .subject-card { min-height: 140px; padding: var(--gap-md) var(--gap-sm); }
  .subject-card h3 { font-size: 1rem; }
  .player-controls { padding: 18px 8px 8px; }
  .now-playing { flex-direction: column; }
  .playlist-thumb { width: 70px; height: 44px; }
}

/* Large displays / Android TV / Smartboards */
@media (min-width: 1600px) {
  html { font-size: 18px; }
}
@media (min-width: 2200px) {
  html { font-size: 22px; }
}

/* --------------------------------------------------------------------------
   17. ANIMATIONS
   -------------------------------------------------------------------------- */
@keyframes shimmer {
  100% { transform: translateX(100%); }
}
@keyframes loaderSlide {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(350%); }
}
@keyframes fadeSlideUp {
  from { opacity: 0; transform: translateY(14px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes spin {
  to { transform: rotate(360deg); }
}
@keyframes toastIn {
  from { opacity: 0; transform: translateY(20px) scale(.95); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}
@keyframes toastOut {
  to { opacity: 0; transform: translateY(10px) scale(.95); }
}
@keyframes pop {
  0% { transform: scale(1); }
  40% { transform: scale(1.3); }
  100% { transform: scale(1); }
}
.bookmarked-pop { animation: pop .35s ease; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}