:root {
    --bg:        #0a0f1e;
    --surface:   #111827;
    --card-bg:   #e8edf8;
    --card-back: #1a2744;
    --gold:      #7aa2f7;
    --gold-lt:   #a9c4ff;
    --teal:      #4a90d9;
    --teal-dk:   #2d6aad;
    --cream:     #e8edf8;
    --ink:       #0a0f1e;
    --muted:     #6b7a99;
    --red:       #f7768e;
    --green:     #9ece6a;
  }

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

  body {
    background: var(--bg);
    font-family: 'Lato', sans-serif;
    color: var(--cream);
    min-height: 100vh;
    overflow-x: hidden;
    position: relative;
    display: flex;
    flex-direction: column;
  }

  main {
    flex: 1;
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
    padding: 40px 20px 80px;
    box-sizing: border-box;
  }

  /* Grain texture overlay */
  body::before {
    content: '';
    position: fixed; inset: 0;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)' opacity='0.04'/%3E%3C/svg%3E");
    pointer-events: none; z-index: 1000; opacity: 0.4;
  }

  /* Decorative corner pattern */
  body::after {
    content: '';
    position: fixed;
    top: 0; right: 0;
    width: 300px; height: 300px;
    background: radial-gradient(circle at top right, rgba(122,162,247,0.08) 0%, transparent 70%);
    pointer-events: none;
  }

  /* ── HEADER ── */
  header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 40px;
    border-bottom: 1px solid rgba(122,162,247,0.2);
    position: relative;
  }

  .logo {
    font-family: 'DM Serif Display', serif;
    font-size: 1.8rem;
    color: var(--gold);
    letter-spacing: 0.02em;
    margin: 0;
    font-weight: normal;
  }
  .logo span { font-style: italic; color: var(--gold-lt); }

  .logo-sub {
    font-family: 'Lato', sans-serif;
    font-size: 0.65rem;
    color: var(--muted);
    letter-spacing: 0.25em;
    text-transform: uppercase;
    margin-top: 1px;
  }

  /* ── NAV TABS ── */
  .nav-tabs {
    display: flex;
    gap: 4px;
    background: rgba(255,255,255,0.04);
    border: 1px solid rgba(122,162,247,0.15);
    border-radius: 40px;
    padding: 4px;
  }

  .nav-tab {
    padding: 8px 20px;
    border-radius: 40px;
    font-size: 0.8rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    cursor: pointer;
    border: none;
    background: transparent;
    color: var(--muted);
    font-family: 'Lato', sans-serif;
    font-weight: 700;
    transition: all 0.25s;
  }
  .nav-tab.active {
    background: var(--gold);
    color: var(--ink);
  }
  .nav-tab:hover:not(.active) { color: var(--cream); }

  /* ── SECTION TITLES ── */
  .section-title {
    font-family: 'DM Serif Display', serif;
    font-size: 1.1rem;
    color: var(--gold);
    letter-spacing: 0.05em;
    margin-bottom: 6px;
  }
  .section-desc {
    font-size: 0.78rem;
    color: var(--muted);
    letter-spacing: 0.08em;
    margin-bottom: 24px;
  }

  /* ── VIEWS ── */
  .view { display: none; }
  .view.active { display: block; }

  /* ── BROWSE VIEW ── */
  .filter-bar {
    display: flex;
    gap: 6px;
    flex-wrap: nowrap;
    margin-bottom: 28px;
    overflow-x: auto;
  }
  .filter-btn {
    padding: 5px 12px;
    border-radius: 40px;
    border: 1px solid rgba(122,162,247,0.25);
    background: transparent;
    color: var(--muted);
    font-size: 0.68rem;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    cursor: pointer;
    font-family: 'Lato', sans-serif;
    font-weight: 700;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 5px;
    white-space: nowrap;
  }
  .type-dot {
    width: 7px;
    height: 7px;
    border-radius: 50%;
    flex-shrink: 0;
  }
  .dot-vowel     { background: #7aa2f7; }
  .dot-consonant { background: #4ad0b4; }
  .dot-special   { background: #bb86fc; }
  .filter-btn[data-filter="all"] {
    padding: 6px 10px;
    font-size: 1rem;
    line-height: 1;
  }
  .filter-btn.active, .filter-btn:hover {
    background: rgba(232,237,248,0.1);
    border-color: #e8edf8;
    color: #e8edf8;
  }
  .filter-btn[data-filter="vowel"].active,
  .filter-btn[data-filter="vowel"]:hover {
    background: rgba(122,162,247,0.15);
    border-color: #7aa2f7;
    color: #7aa2f7;
  }
  .filter-btn[data-filter="consonant"].active,
  .filter-btn[data-filter="consonant"]:hover {
    background: rgba(74,208,180,0.15);
    border-color: #4ad0b4;
    color: #4ad0b4;
  }
  .filter-btn[data-filter="special"].active,
  .filter-btn[data-filter="special"]:hover {
    background: rgba(187,134,252,0.15);
    border-color: #bb86fc;
    color: #bb86fc;
  }

  .letters-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(88px, 1fr));
    gap: 12px;
  }

  .letter-tile {
    background: var(--surface);
    border: 1px solid rgba(122,162,247,0.15);
    border-radius: 12px;
    padding: 16px 8px 12px;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
    overflow: hidden;
  }
  .letter-tile::before {
    content: '';
    position: absolute; inset: 0;
    opacity: 0;
    transition: opacity 0.2s;
  }
  .letter-tile:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(0,0,0,0.4);
  }
  .letter-tile:hover::before { opacity: 1; }

  /* vowel — blue */
  .letter-tile[data-type="vowel"] {
    border-color: rgba(122,162,247,0.35);
    background: linear-gradient(135deg, rgba(122,162,247,0.08) 0%, var(--surface) 60%);
  }
  .letter-tile[data-type="vowel"]:hover { border-color: #7aa2f7; }
  .letter-tile[data-type="vowel"] .tile-roman { color: #7aa2f7; }

  /* consonant — teal */
  .letter-tile[data-type="consonant"] {
    border-color: rgba(74,208,180,0.3);
    background: linear-gradient(135deg, rgba(74,208,180,0.07) 0%, var(--surface) 60%);
  }
  .letter-tile[data-type="consonant"]:hover { border-color: #4ad0b4; }
  .letter-tile[data-type="consonant"] .tile-roman { color: #4ad0b4; }

  /* special — purple */
  .letter-tile[data-type="special"] {
    border-color: rgba(187,134,252,0.3);
    background: linear-gradient(135deg, rgba(187,134,252,0.07) 0%, var(--surface) 60%);
  }
  .letter-tile[data-type="special"]:hover { border-color: #bb86fc; }
  .letter-tile[data-type="special"] .tile-roman { color: #bb86fc; }

  .tile-odia {
    font-family: 'Noto Sans Oriya', serif;
    font-size: 2rem;
    line-height: 1.2;
    color: var(--cream);
    display: block;
    margin-bottom: 6px;
  }
  .tile-roman {
    font-size: 0.7rem;
    color: var(--gold);
    letter-spacing: 0.05em;
    font-weight: 700;
  }
  .tile-type {
    display: none;
  }
  .tile-tag {
    position: absolute;
    top: 6px; right: 6px;
    width: 6px; height: 6px;
    border-radius: 50%;
    background: var(--teal);
    opacity: 0;
  }
  .letter-tile.mastered .tile-tag { opacity: 1; background: var(--green); }
  .letter-tile.learning .tile-tag { opacity: 1; background: var(--gold); }

  /* ── PRACTICE VIEW ── */
  .mode-toggle {
    display: inline-flex;
    gap: 0;
    background: rgba(255,255,255,0.04);
    border: 1px solid rgba(122,162,247,0.2);
    border-radius: 40px;
    padding: 3px;
    margin-bottom: 28px;
  }
  .mode-btn {
    padding: 6px 22px;
    border-radius: 40px;
    border: none;
    background: transparent;
    color: var(--muted);
    font-family: 'Lato', sans-serif;
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    cursor: pointer;
    transition: all 0.2s;
  }
  .mode-btn.active {
    background: var(--gold);
    color: var(--ink);
  }

  .practice-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 32px;
  }

  .practice-controls {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
  }

  .btn {
    padding: 10px 22px;
    border-radius: 8px;
    border: none;
    cursor: pointer;
    font-family: 'Lato', sans-serif;
    font-weight: 700;
    font-size: 0.8rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    transition: all 0.2s;
  }
  .btn-primary { background: var(--gold); color: var(--ink); }
  .btn-primary:hover { background: var(--gold-lt); }
  .btn-outline {
    background: transparent;
    border: 1px solid rgba(122,162,247,0.3);
    color: var(--gold);
  }
  .btn-outline:hover { border-color: var(--gold); background: rgba(122,162,247,0.08); }
  .btn-teal { background: var(--teal); color: #fff; }
  .btn-teal:hover { background: var(--teal-dk); }
  .btn-sm { padding: 7px 14px; font-size: 0.72rem; }

  /* Progress bar */
  .progress-wrap {
    margin-bottom: 18px;
    margin-bottom: 36px;
  }
  .progress-label {
    display: flex;
    justify-content: space-between;
    font-size: 0.72rem;
    color: var(--muted);
    letter-spacing: 0.08em;
    margin-bottom: 8px;
  }
  .progress-bar {
    height: 3px;
    background: rgba(255,255,255,0.07);
    border-radius: 3px;
    overflow: hidden;
  }
  .progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--teal), var(--gold));
    border-radius: 3px;
    transition: width 0.5s ease;
  }

  /* ── FLASHCARD ── */
  .card-arena {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 28px;
  }

  .card-scene {
    width: 100%;
    max-width: 480px;
    height: 300px;
    perspective: 1200px;
    cursor: pointer;
  }

  .card-inner {
    width: 100%;
    height: 100%;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  }

  .card-scene.flipped .card-inner {
    transform: rotateY(180deg);
  }

  .card-face {
    position: absolute; inset: 0;
    backface-visibility: hidden;
    border-radius: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 40px;
  }

  .card-front {
    background: var(--card-bg);
    border: 1px solid rgba(201,147,58,0.4);
    box-shadow: 0 20px 60px rgba(0,0,0,0.5), inset 0 1px 0 rgba(255,255,255,0.3);
    position: relative;
    overflow: hidden;
  }

  /* Palm leaf vein pattern on front */
  .card-front::before {
    content: '';
    position: absolute;
    top: 0; left: 50%;
    transform: translateX(-50%);
    width: 1px;
    height: 100%;
    background: linear-gradient(to bottom, transparent, rgba(180,140,80,0.2), transparent);
  }
  .card-front::after {
    content: '';
    position: absolute; inset: 12px;
    border: 1px solid rgba(180,140,80,0.2);
    border-radius: 12px;
    pointer-events: none;
  }

  .card-odia-letter {
    font-family: 'Noto Sans Oriya', serif;
    font-size: 7rem;
    color: var(--ink);
    line-height: 1;
    text-shadow: 2px 3px 8px rgba(0,0,0,0.15);
    position: relative;
  }

  .card-hint {
    font-size: 0.75rem;
    color: var(--muted);
    letter-spacing: 0.15em;
    text-transform: uppercase;
    position: absolute;
    bottom: 18px;
  }

  .card-back {
    background: var(--card-back);
    border: 1px solid rgba(74,173,160,0.3);
    box-shadow: 0 20px 60px rgba(0,0,0,0.5);
    transform: rotateY(180deg);
  }

  .card-back-letter {
    font-family: 'Noto Sans Oriya', serif;
    font-size: 3.5rem;
    color: var(--teal);
    line-height: 1;
  }

  .back-roman {
    font-family: 'DM Serif Display', serif;
    font-size: 2.2rem;
    color: var(--cream);
    letter-spacing: 0.05em;
  }

  .back-type {
    font-size: 0.72rem;
    color: rgba(255,255,255,0.35);
    letter-spacing: 0.18em;
    text-transform: uppercase;
  }

  .back-example {
    margin-top: 8px;
    font-size: 0.8rem;
    color: rgba(255,255,255,0.5);
    font-style: italic;
    text-align: center;
  }

  /* Rating buttons */
  .rating-buttons {
    display: flex;
    gap: 12px;
    opacity: 0;
    transform: translateY(10px);
    transition: all 0.3s ease 0.4s;
    pointer-events: none;
  }
  .rating-buttons.visible {
    opacity: 1;
    transform: translateY(0);
    pointer-events: all;
  }

  .rate-btn {
    flex: 1;
    max-width: 140px;
    padding: 12px 0;
    border-radius: 10px;
    border: none;
    cursor: pointer;
    font-family: 'Lato', sans-serif;
    font-weight: 700;
    font-size: 0.78rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    transition: all 0.2s;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
  }
  .rate-btn .rate-label { font-size: 0.62rem; opacity: 0.7; font-weight: 400; }
  .rate-hard { background: rgba(247,118,142,0.2); border: 1px solid rgba(247,118,142,0.4); color: #f7768e; }
  .rate-hard:hover { background: rgba(247,118,142,0.35); }
  .rate-good { background: rgba(122,162,247,0.2); border: 1px solid rgba(122,162,247,0.4); color: var(--gold-lt); }
  .rate-good:hover { background: rgba(122,162,247,0.35); }
  .rate-easy { background: rgba(158,206,106,0.2); border: 1px solid rgba(158,206,106,0.4); color: #9ece6a; }
  .rate-easy:hover { background: rgba(158,206,106,0.35); }

  .card-counter {
    font-size: 0.72rem;
    color: var(--muted);
    letter-spacing: 0.15em;
  }

  /* Session complete */
  .session-complete {
    display: none;
    text-align: center;
    padding: 60px 20px;
    animation: fadeUp 0.5s ease;
  }
  .session-complete.visible { display: block; }

  @keyframes fadeUp {
    from { opacity: 0; transform: translateY(20px); }
    to   { opacity: 1; transform: translateY(0); }
  }

  .complete-icon {
    font-size: 4rem;
    margin-bottom: 20px;
  }
  .complete-title {
    font-family: 'DM Serif Display', serif;
    font-size: 2.5rem;
    color: var(--gold);
    margin-bottom: 8px;
  }
  .complete-sub {
    color: var(--muted);
    font-size: 0.9rem;
    margin-bottom: 32px;
  }
  .stats-row {
    display: flex;
    justify-content: center;
    gap: 40px;
    margin-bottom: 36px;
  }
  .stat-box { text-align: center; }
  .stat-num {
    font-family: 'DM Serif Display', serif;
    font-size: 2.2rem;
    color: var(--cream);
  }
  .stat-lbl {
    font-size: 0.68rem;
    color: var(--muted);
    letter-spacing: 0.15em;
    text-transform: uppercase;
    margin-top: 2px;
  }

  /* ── QUIZ VIEW ── */
  .quiz-question {
    text-align: center;
    margin-bottom: 40px;
  }
  .quiz-odia {
    font-family: 'Noto Sans Oriya', serif;
    font-size: 6rem;
    color: var(--cream);
    line-height: 1.1;
    margin-bottom: 12px;
    text-shadow: 0 0 40px rgba(201,147,58,0.2);
  }
  .quiz-prompt {
    font-size: 0.78rem;
    color: var(--muted);
    letter-spacing: 0.15em;
    text-transform: uppercase;
  }

  .quiz-options {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
    max-width: 480px;
    margin: 0 auto 32px;
  }

  .quiz-option {
    padding: 18px 20px;
    background: var(--surface);
    border: 1px solid rgba(201,147,58,0.15);
    border-radius: 12px;
    cursor: pointer;
    text-align: center;
    font-family: 'DM Serif Display', serif;
    font-size: 1.3rem;
    color: var(--cream);
    transition: all 0.2s;
    position: relative;
    overflow: hidden;
  }
  .quiz-option .opt-sub {
    font-family: 'Lato', sans-serif;
    font-size: 0.68rem;
    color: var(--muted);
    font-style: normal;
    display: block;
    margin-top: 2px;
    letter-spacing: 0.08em;
    text-transform: uppercase;
  }
  .quiz-option:hover:not(.answered) {
    border-color: var(--gold);
    background: rgba(201,147,58,0.08);
    transform: translateY(-1px);
  }
  .quiz-option.correct {
    border-color: var(--green);
    background: rgba(158,206,106,0.12);
    color: #9ece6a;
  }
  .quiz-option.wrong {
    border-color: var(--red);
    background: rgba(247,118,142,0.12);
    color: #f7768e;
  }
  .quiz-option.reveal {
    border-color: var(--green);
    background: rgba(39,174,96,0.08);
  }

  .quiz-feedback {
    text-align: center;
    font-size: 0.85rem;
    min-height: 24px;
    margin-bottom: 20px;
    font-weight: 700;
    letter-spacing: 0.05em;
    transition: opacity 0.3s;
  }
  .quiz-feedback.correct { color: #9ece6a; }
  .quiz-feedback.wrong { color: #f7768e; }

  /* ── TOAST ── */
  .toast {
    position: fixed;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%) translateY(20px);
    background: var(--gold);
    color: var(--ink);
    padding: 16px 36px;
    border-radius: 14px;
    font-size: 1.2rem;
    font-weight: 700;
    letter-spacing: 0.06em;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
    z-index: 999;
    white-space: normal;
    max-width: min(320px, calc(100vw - 24px));
    box-shadow: 0 8px 40px rgba(122,162,247,0.4), 0 2px 8px rgba(0,0,0,0.4);
    text-align: center;
  }
  .toast.show {
    opacity: 1;
  }

  /* Decorative divider */
  .divider {
    display: flex;
    align-items: center;
    gap: 16px;
    margin: 32px 0;
    color: rgba(122,162,247,0.2);
    font-size: 0.65rem;
    letter-spacing: 0.3em;
    text-transform: uppercase;
  }
  .divider::before, .divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: rgba(122,162,247,0.15);
  }

  /* Animate in on load */
  .card-scene { animation: fadeUp 0.5s ease; }

  /* Scrollbar */
  ::-webkit-scrollbar { width: 6px; }
  ::-webkit-scrollbar-track { background: var(--bg); }
  ::-webkit-scrollbar-thumb { background: rgba(122,162,247,0.3); border-radius: 3px; }

  /* ── COMING SOON ── */
  .coming-soon {
    margin-top: 32px;
    padding: 14px 20px;
    border: 1px dashed rgba(122,162,247,0.25);
    border-radius: 10px;
    color: var(--muted);
    font-size: 0.82rem;
    text-align: center;
    letter-spacing: 0.04em;
  }

  /* ── FOOTER ── */
  footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 40px;
    border-top: 1px solid rgba(122,162,247,0.15);
    font-size: 0.75rem;
    color: var(--muted);
    font-family: 'Lato', sans-serif;
  }
  footer a {
    color: var(--gold-lt);
    text-decoration: none;
  }
  footer a:hover { text-decoration: underline; }

  /* Mobile */
  @media (max-width: 600px) {
    header {
      padding: 16px 20px;
      flex-direction: column;
      align-items: flex-start;
      gap: 14px;
    }
    .nav-tabs {
      width: 100%;
      justify-content: stretch;
    }
    .nav-tab {
      flex: 1;
      text-align: center;
      padding: 8px 10px;
      font-size: 0.72rem;
    }
    .logo { font-size: 1.4rem; }
    .card-odia-letter { font-size: 5rem; }
    .quiz-odia { font-size: 4.5rem; }
    .practice-header { flex-direction: column; align-items: flex-start; gap: 12px; }
    .practice-controls { width: 100%; }
    main { padding: 24px 16px 60px; }
    .letters-grid { grid-template-columns: repeat(auto-fill, minmax(72px, 1fr)); gap: 8px; }
    footer { flex-direction: column; gap: 6px; padding: 16px 20px; text-align: center; }
  }