/* ============================================
   FILMY FLUTE BOOK — Design Tokens & Styles
   Warm golden-earth palette, Indian music inspired
   ============================================ */

:root {
  /* Type Scale */
  --text-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);
  --text-sm: clamp(0.875rem, 0.8rem + 0.35vw, 1rem);
  --text-base: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);
  --text-lg: clamp(1.125rem, 1rem + 0.75vw, 1.5rem);
  --text-xl: clamp(1.5rem, 1.2rem + 1.25vw, 2.25rem);
  --text-2xl: clamp(2rem, 1.2rem + 2.5vw, 3.5rem);
  --text-3xl: clamp(2.5rem, 1rem + 4vw, 5rem);

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Transitions */
  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);

  /* Content widths */
  --content-narrow: 640px;
  --content-default: 960px;
  --content-wide: 1200px;

  /* Fonts */
  --font-display: 'Zodiak', 'Georgia', serif;
  --font-body: 'Satoshi', 'Inter', sans-serif;
}

/* ---- LIGHT MODE (default) ---- */
:root, [data-theme='light'] {
  --color-bg: #FAF6F0;
  --color-surface: #FFF8F0;
  --color-surface-2: #F5EDE3;
  --color-border: #DDD3C4;
  --color-divider: #E8DFCF;
  --color-text: #2D1B0E;
  --color-text-muted: #8B7355;
  --color-text-faint: #B8A890;
  --color-primary: #B8860B;
  --color-primary-hover: #8B6508;
  --color-primary-active: #6E5006;
  --color-primary-highlight: rgba(184, 134, 11, 0.12);
  --color-accent: #1A5653;
  --color-accent-hover: #0E3D3B;
  --color-tamil: #B8860B;
  --color-hindi: #8B4513;
  --color-telugu: #6B3FA0;
  --color-beginner: #437A22;
  --color-intermediate: #B8860B;
  --color-advanced: #A12C4D;
  --shadow-sm: 0 1px 3px rgba(45, 27, 14, 0.06);
  --shadow-md: 0 4px 12px rgba(45, 27, 14, 0.08);
  --shadow-lg: 0 12px 32px rgba(45, 27, 14, 0.12);
}

/* ---- DARK MODE ---- */
[data-theme='dark'] {
  --color-bg: #1A1612;
  --color-surface: #221D17;
  --color-surface-2: #2A241D;
  --color-border: #3D3529;
  --color-divider: #332C22;
  --color-text: #E8DFD0;
  --color-text-muted: #9B8D7A;
  --color-text-faint: #6B5F50;
  --color-primary: #D4A843;
  --color-primary-hover: #E0BA5A;
  --color-primary-active: #C49A30;
  --color-primary-highlight: rgba(212, 168, 67, 0.15);
  --color-accent: #5DB8B4;
  --color-accent-hover: #7ED0CC;
  --color-tamil: #D4A843;
  --color-hindi: #CC8855;
  --color-telugu: #B680E0;
  --color-beginner: #6DAA45;
  --color-intermediate: #D4A843;
  --color-advanced: #DD6974;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.4);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg: #1A1612;
    --color-surface: #221D17;
    --color-surface-2: #2A241D;
    --color-border: #3D3529;
    --color-divider: #332C22;
    --color-text: #E8DFD0;
    --color-text-muted: #9B8D7A;
    --color-text-faint: #6B5F50;
    --color-primary: #D4A843;
    --color-primary-hover: #E0BA5A;
    --color-primary-active: #C49A30;
    --color-primary-highlight: rgba(212, 168, 67, 0.15);
    --color-accent: #5DB8B4;
    --color-accent-hover: #7ED0CC;
    --color-tamil: #D4A843;
    --color-hindi: #CC8855;
    --color-telugu: #B680E0;
    --color-beginner: #6DAA45;
    --color-intermediate: #D4A843;
    --color-advanced: #DD6974;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.4);
  }
}

/* ============================================
   LAYOUT
   ============================================ */

.container {
  width: 100%;
  max-width: var(--content-wide);
  margin-inline: auto;
  padding-inline: var(--space-6);
}

.container--narrow {
  max-width: var(--content-narrow);
}

.container--default {
  max-width: var(--content-default);
}

/* ============================================
   HEADER
   ============================================ */

.header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: oklch(from var(--color-bg) l c h / 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--color-divider);
  padding: var(--space-4) 0;
}

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.header__logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  text-decoration: none;
  color: var(--color-text);
}

.header__logo svg {
  flex-shrink: 0;
}

.header__title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 500;
  letter-spacing: -0.01em;
}

.header__nav {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.header__nav a {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
}

.header__nav a:hover {
  color: var(--color-text);
  background: var(--color-primary-highlight);
}

.header__nav a.active {
  color: var(--color-primary);
  font-weight: 600;
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
}

.theme-toggle:hover {
  color: var(--color-text);
  background: var(--color-primary-highlight);
}

/* ============================================
   HERO
   ============================================ */

.hero {
  padding: clamp(var(--space-16), 10vw, var(--space-24)) 0;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% 0%, var(--color-primary-highlight), transparent),
    radial-gradient(ellipse 40% 40% at 80% 80%, rgba(26, 86, 83, 0.06), transparent);
  pointer-events: none;
}

.hero__flute {
  margin: 0 auto var(--space-8);
  opacity: 0.85;
}

.hero__heading {
  font-family: var(--font-display);
  font-size: var(--text-3xl);
  font-weight: 500;
  color: var(--color-text);
  letter-spacing: -0.02em;
  margin-bottom: var(--space-4);
  position: relative;
}

.hero__sub {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  max-width: 38ch;
  margin-inline: auto;
  position: relative;
}

/* ============================================
   STATS BAR
   ============================================ */

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: var(--space-4);
  padding: var(--space-8) 0;
}

.stat-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  text-align: center;
}

.stat-card__value {
  font-family: var(--font-display);
  font-size: var(--text-2xl);
  font-weight: 500;
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: var(--space-2);
  font-variant-numeric: tabular-nums lining-nums;
}

.stat-card__label {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

/* ============================================
   SECTION
   ============================================ */

.section {
  padding: clamp(var(--space-12), 6vw, var(--space-20)) 0;
}

.section + .section {
  border-top: 1px solid var(--color-divider);
}

.section__header {
  margin-bottom: var(--space-8);
}

.section__title {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 500;
  color: var(--color-text);
  letter-spacing: -0.01em;
  margin-bottom: var(--space-2);
}

.section__desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

/* ============================================
   LESSON CARD
   ============================================ */

.lessons-grid {
  display: grid;
  gap: var(--space-6);
}

.lesson-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: box-shadow var(--transition-interactive), border-color var(--transition-interactive);
}

.lesson-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary);
}

.lesson-card__header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  padding: var(--space-6);
  cursor: pointer;
  user-select: none;
}

.lesson-card__number {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-full);
  background: var(--color-primary);
  color: #fff;
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 500;
}

.lesson-card__info {
  flex: 1;
  min-width: 0;
}

.lesson-card__song {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 500;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.lesson-card__meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: center;
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.badge {
  display: inline-flex;
  align-items: center;
  padding: 2px var(--space-2);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 500;
  letter-spacing: 0.02em;
}

.badge--tamil { background: rgba(184, 134, 11, 0.12); color: var(--color-tamil); }
.badge--hindi { background: rgba(139, 69, 19, 0.12); color: var(--color-hindi); }
.badge--telugu { background: rgba(107, 63, 160, 0.12); color: var(--color-telugu); }
.badge--beginner { background: rgba(67, 122, 34, 0.1); color: var(--color-beginner); }
.badge--intermediate { background: rgba(184, 134, 11, 0.1); color: var(--color-intermediate); }

.lesson-card__toggle {
  flex-shrink: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  color: var(--color-text-faint);
  transition: transform 300ms cubic-bezier(0.16, 1, 0.3, 1), color var(--transition-interactive);
}

.lesson-card.is-open .lesson-card__toggle {
  transform: rotate(180deg);
  color: var(--color-primary);
}

.lesson-card__body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 400ms cubic-bezier(0.16, 1, 0.3, 1);
}

.lesson-card.is-open .lesson-card__body {
  max-height: 4000px;
}

.lesson-card__content {
  padding: 0 var(--space-6) var(--space-6);
  border-top: 1px solid var(--color-divider);
  padding-top: var(--space-6);
}

/* Lesson content sections */
.lesson-section {
  margin-bottom: var(--space-6);
}

.lesson-section:last-child {
  margin-bottom: 0;
}

.lesson-section__title {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-3);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.lesson-section__title svg {
  flex-shrink: 0;
  width: 16px;
  height: 16px;
}

.notation-block {
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  font-family: 'JetBrains Mono', monospace;
  font-size: var(--text-sm);
  line-height: 1.8;
  white-space: pre-wrap;
  overflow-x: auto;
  color: var(--color-text);
}

.notation-label {
  font-family: var(--font-body);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: var(--space-2);
}

.lesson-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.lesson-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-accent);
  text-decoration: none;
  font-weight: 500;
}

.lesson-link:hover {
  background: var(--color-primary-highlight);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.practice-steps {
  list-style: none;
  counter-reset: step;
}

.practice-steps li {
  counter-increment: step;
  display: flex;
  align-items: baseline;
  gap: var(--space-3);
  padding: var(--space-2) 0;
  font-size: var(--text-sm);
  color: var(--color-text);
}

.practice-steps li::before {
  content: counter(step);
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: var(--radius-full);
  background: var(--color-primary-highlight);
  color: var(--color-primary);
  font-size: var(--text-xs);
  font-weight: 700;
}

.raga-info {
  display: grid;
  gap: var(--space-3);
  font-size: var(--text-sm);
}

.raga-info dt {
  font-weight: 600;
  color: var(--color-text-muted);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.raga-info dd {
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.related-songs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.related-song-tag {
  padding: var(--space-1) var(--space-3);
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

/* ============================================
   EMPTY STATE
   ============================================ */

.empty-state {
  text-align: center;
  padding: var(--space-16) var(--space-6);
  background: var(--color-surface);
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-xl);
}

.empty-state__icon {
  margin: 0 auto var(--space-4);
  opacity: 0.6;
}

.empty-state__title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.empty-state__desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  max-width: 40ch;
  margin-inline: auto;
}

/* ============================================
   SYLLABUS
   ============================================ */

.syllabus-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-3);
}

.syllabus-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  transition: background var(--transition-interactive);
}

.syllabus-item:hover {
  background: var(--color-surface-2);
}

.syllabus-item.is-learned {
  border-color: var(--color-primary);
  background: var(--color-primary-highlight);
}

.syllabus-item__num {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-full);
  background: var(--color-surface-2);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--color-text-muted);
}

.syllabus-item.is-learned .syllabus-item__num {
  background: var(--color-primary);
  color: #fff;
}

.syllabus-item__song {
  font-weight: 500;
  color: var(--color-text);
}

.syllabus-item__film {
  color: var(--color-text-muted);
  font-size: var(--text-xs);
}

/* ============================================
   FLASHCARD
   ============================================ */

.flashcard-area {
  perspective: 1000px;
  min-height: 320px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.flashcard {
  width: 100%;
  max-width: 480px;
  min-height: 280px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 600ms cubic-bezier(0.16, 1, 0.3, 1);
  cursor: pointer;
}

.flashcard.is-flipped {
  transform: rotateY(180deg);
}

.flashcard__face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: var(--radius-xl);
  padding: var(--space-8);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.flashcard__front {
  background: linear-gradient(135deg, var(--color-surface), var(--color-surface-2));
  border: 2px solid var(--color-primary);
  box-shadow: var(--shadow-lg);
}

.flashcard__back {
  background: var(--color-surface);
  border: 2px solid var(--color-accent);
  box-shadow: var(--shadow-lg);
  transform: rotateY(180deg);
  overflow-y: auto;
  align-items: flex-start;
  text-align: left;
}

.flashcard__song-title {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.flashcard__film {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-4);
}

.flashcard__prompt {
  font-size: var(--text-xs);
  color: var(--color-primary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.flashcard__hint {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  margin-top: auto;
  padding-top: var(--space-4);
}

.flashcard-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-4);
  margin-top: var(--space-6);
}

.flashcard-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 600;
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  background: var(--color-surface);
}

.flashcard-btn:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.flashcard-btn--primary {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.flashcard-btn--primary:hover {
  background: var(--color-primary-hover);
  color: #fff;
}

.flashcard-counter {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-align: center;
  margin-top: var(--space-3);
}

/* ============================================
   FILTER TABS
   ============================================ */

.filter-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-6);
}

.filter-tab {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  background: var(--color-surface);
}

.filter-tab:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

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

/* ============================================
   REQUEST A SONG
   ============================================ */

.request-form {
  margin-bottom: var(--space-8);
}

.request-input-row {
  display: flex;
  gap: var(--space-3);
  margin-bottom: var(--space-3);
}

.request-input {
  flex: 1;
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-text);
  outline: none;
}

.request-input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-highlight);
}

.request-input::placeholder {
  color: var(--color-text-faint);
}

.request-submit {
  flex-shrink: 0;
  padding: var(--space-3) var(--space-6);
  background: var(--color-primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 600;
  white-space: nowrap;
}

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

.request-hint {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

.request-hint strong {
  color: var(--color-primary);
}

.request-queue {
  display: grid;
  gap: var(--space-3);
}

.request-item {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  animation: fadeUp 400ms cubic-bezier(0.16, 1, 0.3, 1) both;
}

.request-item__icon {
  flex-shrink: 0;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  background: var(--color-primary-highlight);
  color: var(--color-primary);
}

.request-item__info {
  flex: 1;
  min-width: 0;
}

.request-item__url {
  font-size: var(--text-sm);
  color: var(--color-accent);
  word-break: break-all;
  text-decoration: none;
}

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

.request-item__time {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

.request-item__status {
  flex-shrink: 0;
  padding: 2px var(--space-3);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
  background: rgba(184, 134, 11, 0.1);
  color: var(--color-primary);
}

.request-item__remove {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-full);
  color: var(--color-text-faint);
  font-size: var(--text-sm);
}

.request-item__remove:hover {
  background: rgba(161, 44, 77, 0.1);
  color: var(--color-accent);
}

.request-empty {
  text-align: center;
  padding: var(--space-12) var(--space-6);
}

.request-toast {
  position: fixed;
  bottom: 80px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: var(--color-text);
  color: var(--color-bg);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  opacity: 0;
  pointer-events: none;
  transition: opacity 300ms, transform 300ms;
  z-index: 200;
}

.request-toast.is-visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

@media (max-width: 640px) {
  .request-input-row {
    flex-direction: column;
  }
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
  padding: var(--space-8) 0;
  border-top: 1px solid var(--color-divider);
  text-align: center;
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

/* ============================================
   RESPONSIVE
   ============================================ */

/* Mobile bottom nav */
.mobile-nav {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: oklch(from var(--color-bg) l c h / 0.95);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--color-divider);
  padding: var(--space-2) 0;
  padding-bottom: max(var(--space-2), env(safe-area-inset-bottom));
}

.mobile-nav__item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  font-size: 11px;
  font-weight: 500;
  color: var(--color-text-muted);
  text-decoration: none;
  padding: var(--space-1) var(--space-2);
}

.mobile-nav__item.active {
  color: var(--color-primary);
}

@media (max-width: 640px) {
  .header__nav a:not([data-theme-toggle]) { display: none; }
  .hero { padding: var(--space-12) 0; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .syllabus-grid { grid-template-columns: 1fr; }
  .lesson-card__header { padding: var(--space-4); }
  .lesson-card__content { padding: 0 var(--space-4) var(--space-4); padding-top: var(--space-4); }
  .flashcard__face { padding: var(--space-6); }
  .mobile-nav { display: flex; justify-content: space-around; }
  .footer { padding-bottom: calc(var(--space-8) + 64px); }
}

/* ============================================
   VIEW TOGGLE (Lessons / Flashcards / Syllabus)
   ============================================ */

.view { display: none; }
.view.is-active { display: block; }

/* ============================================
   ANIMATIONS
   ============================================ */

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

.animate-in {
  animation: fadeUp 500ms cubic-bezier(0.16, 1, 0.3, 1) both;
}

.lesson-card { animation: fadeUp 500ms cubic-bezier(0.16, 1, 0.3, 1) both; }
.lesson-card:nth-child(2) { animation-delay: 80ms; }
.lesson-card:nth-child(3) { animation-delay: 160ms; }
.lesson-card:nth-child(4) { animation-delay: 240ms; }
.lesson-card:nth-child(5) { animation-delay: 320ms; }