:root {
    --navy: #1b2a4a;
    --navy-light: #2c3e60;
    --accent: #FA7049;
    --accent-hover: #fb8d6d;
    --bg: #f0f2f5;
    --card: #ffffff;
    --text: #1b2a4a;
    --text-muted: #6b7b8d;
    --border: #d0d5dd;
    --error: #dc3545;
    --success: #28a745;
    /* Typography scale */
    --fs-2xs: 0.625rem;
    --fs-xs: 0.75rem;
    --fs-sm: 0.85rem;
    --fs-base: 0.95rem;
    --fs-md: 1rem;
    --fs-lg: 1.15rem;
    --fs-xl: 1.35rem;
    --fs-2xl: 1.6rem;
    --fs-3xl: 2rem;
  }
  * { margin: 0; padding: 0; box-sizing: border-box; }
  body, button, input, select, textarea {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  }
  body {
    background: var(--bg);
    color: var(--text);
    font-size: var(--fs-base);
    min-height: 100vh;
    overflow: hidden;
  }
  .screen {
    display: none; width: 100vw; height: 100vh;
    flex-direction: column; align-items: center; justify-content: center;
    animation: fadeIn 0.3s ease;
  }
  .screen.active { display: flex; }
  .screen:not(.active) { content-visibility: hidden; }
  .screen.has-tabs { padding-bottom: 64px !important; }
  @keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
  }

  /* ── Bottom Tab Bar ── */
  .tab-bar {
    position: fixed; bottom: 0; left: 0; right: 0;
    height: 60px; background: var(--card);
    border-top: 1px solid var(--border);
    display: none; justify-content: space-around; align-items: center;
    z-index: 100; padding: 0 0.5rem;
    box-shadow: 0 -2px 10px rgba(27,42,74,0.06);
  }
  .tab-bar.visible { display: flex; }
  .tab-btn {
    flex: 1; display: flex; flex-direction: column; align-items: center;
    gap: 2px; background: none; border: none; color: var(--text-muted);
    font-size: var(--fs-xs); cursor: pointer;
    padding: 0.4rem 0; transition: color 0.2s; position: relative;
  }
  .tab-btn .tab-icon { width: 24px; height: 24px; display: flex; align-items: center; justify-content: center; }
  .tab-btn .tab-icon svg { width: 24px; height: 24px; fill: var(--text-muted); transition: fill 0.2s; }
  .tab-btn.active .tab-icon svg { fill: url(#tab-gradient); }
  .tab-btn.active { color: var(--accent); }
  .tab-btn.active::after {
    content: ''; position: absolute; top: -1px; left: 25%; right: 25%;
    height: 2px; background: var(--accent); border-radius: 0 0 2px 2px;
  }

  /* ── Unified Button System ── */
  .btn, .btn-play, .btn-ok, .btn-secondary {
    display: inline-flex; align-items: center; justify-content: center;
    gap: 0.4rem; padding: 0.7rem 1.5rem; font-size: var(--fs-base);
    font-weight: 600; border-radius: 8px;
    cursor: pointer; transition: all 0.2s; border: none;
    min-height: 44px; text-decoration: none;
  }
  .btn-primary, .btn-play, .btn-ok {
    background: var(--accent); color: #fff;
    box-shadow: 0 2px 8px rgba(250,112,73,0.2);
  }
  .btn-primary:hover, .btn-play:hover, .btn-ok:hover { background: var(--accent-hover); transform: translateY(-1px); box-shadow: 0 4px 12px rgba(250,112,73,0.3); }
  .btn-outline, .btn-secondary {
    background: var(--card); color: var(--text); border: 1px solid var(--border);
  }
  .btn-outline:hover, .btn-secondary:hover { border-color: var(--accent); color: var(--accent); }
  .btn-ghost {
    background: none; color: var(--text-muted); border: none; padding: 0.5rem 1rem;
  }
  .btn-ghost:hover { color: var(--accent); }
  .btn-full { width: 100%; }
  .btn-sm { padding: 0.45rem 1rem; font-size: var(--fs-sm); min-height: 36px; }
  .btn-row { display: flex; gap: 0.6rem; flex-wrap: wrap; justify-content: center; width: 100%; margin-top: 0.3rem; }

  /* ── Screen Header (non-game) ── */
  .screen-header {
    width: 100%; max-width: 550px; display: flex; align-items: center;
    padding: 0 0.5rem; margin-bottom: 0.5rem;
  }
  .screen-header h2 {
    flex: 1; text-align: center; font-size: var(--fs-lg); color: var(--navy);
    font-variant: small-caps; letter-spacing: 1px;
  }
  .btn-back {
    background: none; border: none; color: var(--text-muted); font-size: var(--fs-xl);
    cursor: pointer; padding: 0.3rem; transition: color 0.2s; line-height: 1;
  }
  .btn-back:hover { color: var(--accent); }
  .header-spacer { width: 28px; }

  /* Home Banner */
  .home-banner {
    display: flex; align-items: center; justify-content: space-between;
    width: 100%; max-width: 420px; padding: 0.6rem 1rem;
    background: linear-gradient(135deg, var(--navy), var(--navy-light));
    color: #fff; border-radius: 10px; text-decoration: none;
    font-size: var(--fs-sm); font-weight: 500;
    transition: opacity 0.2s; cursor: pointer;
  }
  .home-banner:hover { opacity: 0.9; }
  .hb-text { flex: 1; }
  .hb-arrow { font-size: var(--fs-lg); margin-left: 0.5rem; }

  /* Home / Landing */
  #screen-home { gap: 0.8rem; padding: 1.5rem 1.5rem 1rem; justify-content: flex-start; padding-top: 2.5rem; overflow-y: auto; -webkit-overflow-scrolling: touch; }
  #screen-home h1 {
    font-size: clamp(1.5rem, 4vw, 2.5rem);
    color: var(--navy); font-variant: small-caps;
    margin-bottom: 0.3rem;
  }
  .home-welcome-card {
    width: 100%; max-width: 420px; background: var(--card);
    border: 1px solid var(--border); border-radius: 12px;
    padding: 1rem 1.2rem; display: flex; align-items: center; gap: 0.8rem;
    cursor: pointer; transition: box-shadow 0.2s;
  }
  .home-welcome-card:hover { box-shadow: 0 2px 12px rgba(0,0,0,0.08); }
  .home-welcome-card .hw-avatar {
    width: 44px; height: 44px; border-radius: 50%;
    background: var(--navy); color: #fff;
    display: flex; align-items: center; justify-content: center;
    font-size: var(--fs-xl); font-weight: bold; flex-shrink: 0;
  }
  .home-welcome-card .hw-info { display: flex; flex-direction: column; flex: 1; min-width: 0; }
  .home-welcome-card .hw-name { font-weight: 600; color: var(--navy); font-size: var(--fs-md); }
  .home-welcome-card .hw-meta { font-size: var(--fs-xs); color: var(--text-muted); }
  .home-welcome-card .hw-medals { display: flex; gap: 0.6rem; flex-shrink: 0; align-items: center; }
  .home-welcome-card .hw-medal { display: flex; flex-direction: column; align-items: center; gap: 0.15rem; font-size: var(--fs-2xs); color: var(--text-muted); line-height: 1.1; text-align: center; max-width: 56px; }
  .home-welcome-card .hw-medal-icon { font-size: 1.4rem; }
  .home-welcome-card .hw-streak {
    background: linear-gradient(135deg, var(--accent), #fb8d6d);
    color: #fff; padding: 0.2rem 0.6rem; border-radius: 999px;
    font-size: var(--fs-xs); font-weight: 600; white-space: nowrap;
  }
  .home-section-label {
    font-size: var(--fs-xs); text-transform: uppercase; letter-spacing: 2px;
    color: var(--text-muted); margin-top: 0.5rem; width: 100%; max-width: 420px;
  }
  .home-input-row {
    display: flex; gap: 0.5rem; align-items: stretch;
  }
  .home-input-row input {
    flex: 1; padding: 0.6rem 0.8rem; font-size: var(--fs-base);
    border: 1px solid var(--border); border-radius: 6px;
    outline: none; min-width: 0;
  }
  .home-input-row input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(250,112,73,0.1); }
  .home-input-row input.error { border-color: var(--error); box-shadow: 0 0 0 3px rgba(220,53,69,0.1); }
  .btn-play { width: 100%; }
  .home-register-hint {
    font-size: var(--fs-xs); color: var(--text-muted); text-align: center;
    line-height: 1.4;
  }
  .home-register-hint b { color: var(--accent); }

  /* Details */
  #screen-details { padding: 2rem; }
  .details-form {
    width: 100%; max-width: 460px;
    display: flex; flex-direction: column; gap: 0.6rem;
  }
  .details-form label { font-size: var(--fs-md); color: var(--text-muted); margin-top: 0.4rem; }
  .details-form input[type="text"],
  .details-form input[type="email"],
  .details-form input[type="tel"] {
    padding: 0.7rem 0.9rem; font-size: var(--fs-md);
    border: 2px solid var(--border); background: #fff;
    color: var(--text); outline: none;
    border-radius: 4px; transition: border-color 0.2s;
  }
  .details-form input:focus { border-color: var(--accent); }
  .details-form input.error { border-color: var(--error); background: #fff5f5; }
  .radio-group { display: flex; gap: 2rem; margin-top: 0.3rem; }
  .radio-group label {
    display: flex; align-items: center; gap: 0.5rem; cursor: pointer;
    font-size: var(--fs-md); color: var(--text); margin-top: 0;
  }
  .radio-group input[type="radio"] { accent-color: var(--accent); width: 18px; height: 18px; }
  .disclaimer {
    font-size: var(--fs-sm); color: var(--text-muted);
    text-align: center; margin-top: 1.2rem; line-height: 1.4;
  }

  /* Countdown */
  #screen-countdown { flex-direction: column; gap: 0.5rem; }
  .countdown-title {
    font-size: clamp(1.2rem, 3vw, 2rem);
    color: var(--text-muted); font-variant: small-caps;
  }
  .countdown-number {
    font-size: clamp(5rem, 15vw, 10rem);
    font-weight: 200; color: var(--navy); line-height: 1;
  }

  /* Game Screen */
  #screen-game { padding: 0; justify-content: flex-start; }
  .game-header {
    width: 100%; display: flex; justify-content: space-between;
    align-items: center; padding: 0.5rem 1rem;
    background: var(--navy); color: #fff; z-index: 10;
    flex-wrap: wrap; gap: 0.3rem;
  }
  .game-title-label { font-size: var(--fs-xs); color: rgba(255,255,255,0.7); text-transform: uppercase; letter-spacing: 1px; width: 100%; text-align: center; order: -1; }
  .game-timer {
    font-size: clamp(1rem, 2.5vw, 1.4rem);
    font-variant-numeric: tabular-nums; color: #fff; font-weight: bold;
  }
  .game-timer.paused { opacity: 0.5; }
  .game-instructions { font-size: clamp(var(--fs-xs), 1.5vw, var(--fs-sm)); color: rgba(255,255,255,0.7); }
  .game-progress { font-size: clamp(var(--fs-sm), 1.5vw, var(--fs-md)); color: rgba(255,255,255,0.9); }
  .btn-back-game {
    background: rgba(255,255,255,0.15); border: 1px solid rgba(255,255,255,0.3);
    color: #fff; padding: 0.3rem 0.7rem; font-size: var(--fs-sm);
    cursor: pointer; border-radius: 6px;
    transition: all 0.2s; white-space: nowrap;
  }
  .btn-back-game:hover { background: rgba(255,255,255,0.25); }
  .btn-stop-game { padding: 0.3rem 0.5rem; background: rgba(231,76,60,0.3); border-color: rgba(231,76,60,0.5); }
  .btn-stop-game:hover { background: rgba(231,76,60,0.5); }

  .game-area {
    flex: 1; width: 100%;
    display: flex; gap: 0; position: relative;
    overflow: hidden;
  }
  .game-panel {
    flex: 1; display: flex; flex-direction: column;
    align-items: center; padding: 0.3rem;
    min-width: 0;
  }
  .panel-label {
    font-size: clamp(0.65rem, 1.2vw, 0.85rem);
    color: var(--text-muted); margin-bottom: 0.2rem;
    text-transform: uppercase; letter-spacing: 2px;
  }
  .game-divider { width: 1px; background: var(--border); align-self: stretch; }
  canvas {
    background: #ffffff;
    border: 1px solid var(--border);
    cursor: crosshair;
    max-width: 100%;
  }

  /* Palette — sidebar on desktop, bottom bar on mobile */
  .palette {
    display: flex; flex-direction: column;
    gap: 4px; padding: 6px;
    background: var(--card);
    border-left: 1px solid var(--border);
    overflow-y: auto; overflow-x: hidden;
    width: 80px; min-width: 80px;
    align-items: center;
  }
  .pal-btn {
    display: flex; flex-direction: column;
    align-items: center; justify-content: center;
    width: 66px; height: 56px;
    border: 2px solid var(--border);
    background: #fff; color: var(--text);
    cursor: pointer;
    border-radius: 6px; transition: all 0.15s;
    padding: 3px; gap: 1px; flex-shrink: 0;
  }
  .pal-btn:hover { border-color: var(--navy); background: #f0f4ff; }
  .pal-btn.active { border-color: var(--accent); background: #fff5ee; box-shadow: 0 0 0 2px rgba(250,112,73,0.25); }
  .pal-btn .pal-sym { width: 28px; height: 28px; display: flex; align-items: center; justify-content: center; color: var(--navy); }
  .pal-btn .pal-sym svg { width: 100%; height: 100%; }
  .pal-btn .pal-lbl { font-size: var(--fs-2xs); color: var(--text-muted); white-space: nowrap; }
  .pal-btn .pal-cnt { font-size: var(--fs-2xs); color: var(--accent); font-weight: bold; }

  /* Score */
  #screen-score { padding: 1.5rem; gap: 0.8rem; overflow-y: auto; justify-content: flex-start; padding-top: 1rem; }
  #screen-quiz-result { padding: 1.5rem; gap: 0.8rem; overflow-y: auto; justify-content: flex-start; padding-top: 1rem; }
  .score-title { font-size: var(--fs-xl); color: var(--text-muted); font-variant: small-caps; }
  .score-value {
    font-size: clamp(var(--fs-2xl), 5vw, var(--fs-3xl)); color: var(--navy); font-weight: bold;
    animation: scoreReveal 0.6s ease;
  }
  @keyframes scoreReveal {
    0% { opacity: 0; transform: scale(0.5); }
    60% { transform: scale(1.05); }
    100% { opacity: 1; transform: scale(1); }
  }

  /* Stats Tab Screen */
  #screen-stats { padding: 1.5rem; gap: 0.8rem; overflow-y: auto; justify-content: flex-start; padding-top: 1rem; }
  .stats-card {
    width: 100%; max-width: 420px; background: var(--card);
    border: 1px solid var(--border); border-radius: 12px;
    padding: 1rem 1.2rem; display: flex; flex-direction: column; gap: 0.5rem;
  }
  .stats-card h3 { font-size: var(--fs-sm); color: var(--text-muted); text-transform: uppercase; letter-spacing: 1px; margin: 0; }
  .stats-row {
    display: flex; justify-content: space-between; align-items: center;
    padding: 0.4rem 0; border-bottom: 1px solid var(--bg);
  }
  .stats-row:last-child { border-bottom: none; }
  .stats-label { font-size: var(--fs-base); color: var(--text); }
  .stats-val { font-size: var(--fs-base); font-weight: 600; color: var(--navy); }
  .stats-streak-grid {
    display: grid; grid-template-columns: 1fr 1fr; gap: 0.6rem;
  }
  .stats-streak-grid--2col { grid-template-columns: repeat(2, 1fr); }
  .stats-streak-grid--4col { grid-template-columns: repeat(4, 1fr); margin-top: 0.5rem; }
  .stats-streak-item {
    text-align: center; padding: 0.6rem;
    background: var(--bg); border-radius: 8px;
  }
  .stats-streak-item .ss-val { font-size: var(--fs-2xl); font-weight: 700; color: var(--navy); }
  .stats-streak-item .ss-lbl { font-size: var(--fs-xs); color: var(--text-muted); }

  /* Profile Tab Screen */
  #screen-profile { padding: 1.5rem; gap: 0.8rem; overflow-y: auto; justify-content: flex-start; padding-top: 1rem; }
  .profile-card {
    width: 100%; max-width: 480px; background: var(--card);
    border: 1px solid var(--border); border-radius: 12px;
    padding: 1.2rem; display: flex; flex-direction: column; gap: 0.8rem;
  }
  .profile-avatar-row {
    display: flex; align-items: center; gap: 1rem;
  }
  .profile-avatar {
    width: 56px; height: 56px; border-radius: 50%;
    background: var(--navy); color: #fff;
    display: flex; align-items: center; justify-content: center;
    font-size: var(--fs-2xl); font-weight: bold; flex-shrink: 0;
  }
  .profile-info { display: flex; flex-direction: column; }
  .profile-info .p-name { font-weight: 600; font-size: var(--fs-lg); color: var(--navy); }
  .profile-info .p-detail { font-size: var(--fs-sm); color: var(--text-muted); }
  .profile-lang-row {
    display: flex; align-items: center; gap: 0.5rem;
  }
  .avatar-picker-label { font-size: var(--fs-xs); font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.03em; }
  .avatar-symbol-grid { display: flex; gap: 0.3rem; flex-wrap: wrap; }
  .avatar-sym-btn {
    width: 40px; height: 40px; border-radius: 8px; border: 2px solid var(--border);
    background: var(--card); cursor: pointer; display: flex; align-items: center; justify-content: center;
    font-size: 1.1rem; color: var(--navy); transition: all 0.15s;
  }
  .avatar-sym-btn:hover { border-color: var(--navy); }
  .avatar-sym-btn.selected { border-color: var(--accent); background: rgba(250,112,73,0.1); }
  .avatar-sym-btn .sym-svg { width: 22px; height: 22px; }
  .avatar-sym-btn--letter { font-weight: bold; font-size: 1.2rem; }
  .avatar-color-grid { display: flex; gap: 0.3rem; flex-wrap: wrap; }
  .avatar-color-btn {
    width: 32px; height: 32px; border-radius: 50%; border: 2px solid transparent;
    cursor: pointer; transition: all 0.15s;
  }
  .avatar-color-btn:hover { transform: scale(1.15); }
  .avatar-color-btn.selected { border-color: var(--navy); box-shadow: 0 0 0 2px #fff, 0 0 0 4px var(--navy); }
  .avatar-preview {
    width: 48px; height: 48px; border-radius: 50%; display: flex; align-items: center;
    justify-content: center; font-size: 1.5rem; color: #fff; font-weight: bold; flex-shrink: 0;
  }
  .avatar-preview .sym-svg { width: 26px; height: 26px; color: #fff; }
  .profile-lang-row label { font-size: var(--fs-sm); color: var(--text-muted); }
  .profile-lang-row select {
    padding: 0.4rem 0.8rem; font-size: var(--fs-base);
    border: 1px solid var(--border); border-radius: 6px;
    background: #fff; color: var(--text);
    cursor: pointer; outline: none; flex: 1;
  }
  .profile-actions { display: flex; flex-direction: column; gap: 0.5rem; }
  .profile-guest-msg {
    text-align: center; color: var(--text-muted); font-size: var(--fs-base);
    padding: 1rem 0;
  }
  .top10-title { font-size: var(--fs-lg); color: var(--text-muted); font-variant: small-caps; margin-top: 0.5rem; }
  .top10-list { width: 100%; max-width: 550px; }
  .top10-row { display: flex; padding: 0.4rem 0.8rem; font-size: var(--fs-base); align-items: center; }
  .top10-row:nth-child(even) { background: rgba(27,42,74,0.04); }
  .top10-row.highlight { background: rgba(250,112,73,0.1); color: var(--accent); font-weight: bold; }
  .top10-rank { width: 36px; text-align: center; }
  .top10-name { flex: 1; }
  .top10-score { width: 140px; text-align: right; }

  /* Daily badge */
  .daily-badge {
    background: var(--card); border: 1px solid var(--navy);
    color: var(--navy); padding: 0.3rem 1rem;
    border-radius: 999px; font-size: var(--fs-sm);
    margin-bottom: 1.2rem; letter-spacing: 1px;
    text-align: center; line-height: 1.4;
  }
  .daily-badge .daily-date {
    display: block; font-weight: 600;
  }
  .home-lang-picker {
    display: flex; gap: 0.5rem; justify-content: center; margin-bottom: 1rem;
  }
  .lang-btn {
    display: flex; align-items: center; gap: 0.4rem;
    padding: 0.5rem 1rem; border-radius: 999px;
    border: 2px solid var(--border); background: var(--card);
    font-size: var(--fs-sm); font-weight: 600; color: var(--navy);
    cursor: pointer; transition: all 0.15s;
  }
  .lang-btn:hover, .lang-btn.active { border-color: var(--accent); background: #fff4f0; }
  .lang-flag { font-size: 1.1rem; }
  /* Engagement nudges */
  .streak-warning {
    width: 100%; max-width: 420px;
    background: linear-gradient(135deg, #fff3cd, #ffeeba); border: 1px solid #ffc107;
    color: #856404; padding: 0.5rem 1rem; border-radius: 10px;
    font-size: var(--fs-sm); font-weight: 500; text-align: center;
    margin-bottom: 0.5rem; animation: pulse 2s ease-in-out infinite;
  }
  @keyframes pulse { 0%,100% { transform: scale(1); } 50% { transform: scale(1.02); } }
  .achievement-nudge {
    width: 100%; max-width: 420px;
    background: var(--card); border: 1px solid var(--accent);
    color: var(--text); padding: 0.4rem 1rem; border-radius: 10px;
    font-size: var(--fs-xs); text-align: center; margin-bottom: 0.5rem;
  }
  .daily-players {
    width: 100%; max-width: 420px;
    font-size: var(--fs-xs); color: var(--text-muted);
    text-align: center; margin-bottom: 0.3rem;
  }

  /* Leaderboard / Rankings */
  #screen-rankings { padding: 1.5rem; gap: 0.8rem; overflow-y: auto; justify-content: flex-start; padding-top: 1rem; }
  #screen-leaderboard { padding: 1.5rem; gap: 0.8rem; }
  .lb-tabs {
    display: flex; gap: 0; border-bottom: 2px solid var(--border);
    width: 100%; max-width: 550px;
  }
  .lb-tab {
    flex: 1; background: none; border: none; color: var(--text-muted);
    font-size: var(--fs-base); padding: 0.6rem 0.8rem; cursor: pointer;
    font-variant: small-caps; letter-spacing: 1px;
    transition: all 0.2s; border-bottom: 2px solid transparent; margin-bottom: -2px;
  }
  .lb-tab.active { color: var(--accent); border-bottom-color: var(--accent); }
  .lb-tab:hover { color: var(--text); }
  .rank-game-select {
    width: 100%; padding: 0.5rem 0.8rem; font-size: var(--fs-base);
    border: 2px solid var(--border); border-radius: 8px; background: var(--card);
    color: var(--navy); font-weight: 600; cursor: pointer;
    appearance: none; -webkit-appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%231b2a4a' stroke-width='2' fill='none'/%3E%3C/svg%3E");
    background-repeat: no-repeat; background-position: right 0.8rem center;
  }
  .rank-game-select:focus { border-color: var(--accent); outline: none; }
  .lb-list { width: 100%; max-width: 550px; max-height: 50vh; overflow-y: auto; }
  .lb-row { display: flex; padding: 0.4rem 0.8rem; font-size: var(--fs-base); align-items: center; gap: 0.5rem; }
  .lb-row:nth-child(even) { background: rgba(27,42,74,0.04); }
  .lb-row.highlight { background: rgba(250,112,73,0.1); color: var(--accent); font-weight: bold; }
  .lb-rank { width: 36px; text-align: center; }
  .lb-name { flex: 1; }
  .lb-score { width: 130px; text-align: right; }
  .lb-date { width: 80px; text-align: right; color: var(--text-muted); font-size: var(--fs-sm); }
  .lb-empty {
    text-align: center; color: var(--text-muted); padding: 2.5rem 1rem; font-style: italic;
    font-size: var(--fs-sm); line-height: 1.6;
  }
  .lb-empty::before {
    content: '\1F3C6'; display: block; font-size: 2rem; font-style: normal; margin-bottom: 0.5rem; opacity: 0.3;
  }

  /* Streak & Gamification */
  .streak-badge {
    display: inline-flex; align-items: center; gap: 0.4rem;
    background: linear-gradient(135deg, var(--accent), #fb8d6d);
    color: #fff; padding: 0.3rem 1rem; border-radius: 999px;
    font-size: var(--fs-sm); font-weight: 600; letter-spacing: 0.5px;
    animation: pulseGlow 2s ease-in-out infinite;
  }
  .streak-badge.hidden { display: none; }
  @keyframes pulseGlow {
    0%, 100% { box-shadow: 0 0 0 0 rgba(250,112,73,0.3); }
    50% { box-shadow: 0 0 12px 4px rgba(250,112,73,0.15); }
  }
  .xp-bar-wrap {
    width: 100%; max-width: 550px; height: 8px;
    background: var(--border); border-radius: 99px; overflow: hidden;
    margin: 0.3rem 0;
  }
  .xp-bar {
    height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), #fb8d6d);
    border-radius: 99px; transition: width 1s ease;
  }
  .xp-label { font-size: var(--fs-xs); color: var(--text-muted); }
  .achievements {
    display: flex; flex-direction: column; gap: 0.5rem;
    max-width: 550px; margin: 0.3rem 0; width: 100%;
  }
  .ach-group {
    background: var(--card); border: 1px solid var(--border); border-radius: 10px;
    padding: 0.5rem 0.7rem;
  }
  .ach-group-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 0.3rem; cursor: pointer; user-select: none; }
  .ach-group-header .ach-toggle { font-size: var(--fs-xs); color: var(--text-muted); transition: transform 0.2s; display: inline-block; }
  .ach-group.collapsed .ach-group-header .ach-toggle { transform: rotate(-90deg); }
  .ach-group.collapsed .ach-group-items { display: none; }
  .ach-group.collapsed .ach-group-header { margin-bottom: 0; }
  .ach-group-title {
    font-size: var(--fs-xs); font-weight: 600; color: var(--navy);
    letter-spacing: 0.02em;
  }
  .ach-group-count { font-size: var(--fs-2xs); color: var(--text-muted); }
  .ach-group-items { display: flex; flex-direction: column; gap: 0.25rem; }
  .achievement {
    display: flex; align-items: center; gap: 0.4rem;
    padding: 0.2rem 0; font-size: var(--fs-xs); color: var(--text-muted);
    position: relative;
  }
  .achievement.earned { color: var(--navy); }
  .achievement.earned .ach-icon { color: var(--accent); }
  .achievement.tier-bronze .ach-icon { color: #cd7f32; }
  .achievement.tier-silver .ach-icon { color: #8a9bae; }
  .achievement.tier-gold .ach-icon { color: #daa520; }
  .achievement.tier-platinum .ach-icon { color: #b0c4de; background: linear-gradient(135deg, #7ec8e3, #b0c4de, #e0e0e0); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
  .achievement.tier-special .ach-icon { color: var(--accent); }
  .achievement.hidden-ach { opacity: 0.4; }
  .achievement .ach-icon { font-size: var(--fs-md); width: 1.5em; text-align: center; flex-shrink: 0; }
  .achievement .ach-name { flex: 1; }
  .achievement .ach-check { color: var(--accent); font-size: var(--fs-xs); flex-shrink: 0; }
  .achievement .ach-tip {
    display: none; position: absolute; bottom: 100%; left: 50%; transform: translateX(-50%);
    background: var(--navy); color: #fff; font-size: var(--fs-xs);
    padding: 0.3rem 0.6rem; border-radius: 6px; white-space: nowrap;
    z-index: 10; margin-bottom: 4px; pointer-events: none;
  }
  .achievement .ach-tip::after {
    content: ''; position: absolute; top: 100%; left: 50%; transform: translateX(-50%);
    border: 4px solid transparent; border-top-color: var(--navy);
  }
  .achievement:hover .ach-tip, .achievement:active .ach-tip { display: block; }
  /* Toast notification */
  .toast {
    position: fixed; bottom: 2rem; left: 50%; transform: translateX(-50%) translateY(100px);
    background: var(--navy); color: #fff; padding: 0.8rem 1.5rem;
    border-radius: 10px; font-size: var(--fs-base); z-index: 1000;
    opacity: 0; transition: all 0.4s ease; pointer-events: none;
    box-shadow: 0 4px 20px rgba(27,42,74,0.3);
  }
  .toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
  /* Confetti canvas */
  #confetti-canvas {
    position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    pointer-events: none; z-index: 999;
    display: none;
  }
  #confetti-canvas.active { display: block; }
  /* Points animation */
  .points-popup {
    position: fixed; top: 40%; left: 50%; transform: translate(-50%, -50%);
    font-size: 2.5rem; font-weight: bold; color: var(--accent);
    z-index: 998; pointer-events: none;
    animation: pointsFloat 1.5s ease forwards;
  }
  @keyframes pointsFloat {
    0% { opacity: 1; transform: translate(-50%, -50%) scale(0.5); }
    30% { opacity: 1; transform: translate(-50%, -70%) scale(1.2); }
    100% { opacity: 0; transform: translate(-50%, -120%) scale(0.8); }
  }
  /* Quiz combo indicator */
  .quiz-combo {
    text-align: center; font-size: var(--fs-sm); color: var(--accent);
    font-weight: 600; min-height: 1.2em;
  }
  /* Odoo sync indicator */
  .sync-status {
    font-size: var(--fs-xs); color: var(--text-muted);
    display: flex; align-items: center; gap: 0.3rem;
  }
  .sync-dot {
    width: 6px; height: 6px; border-radius: 50%;
    background: var(--success); display: inline-block;
  }
  .sync-dot.error { background: var(--error); }
  .sync-dot.pending { background: var(--accent); animation: blink 1s infinite; }
  @keyframes blink { 50% { opacity: 0.3; } }

  /* Pause Screen */
  .pause-card {
    background: var(--card); border: 1px solid var(--border);
    border-radius: 16px; padding: 2.5rem; text-align: center;
    display: flex; flex-direction: column; align-items: center; gap: 1rem;
    max-width: 380px; width: 90%;
    box-shadow: 0 8px 30px rgba(27,42,74,0.12);
  }
  .pause-icon { font-size: 3rem; }
  .pause-card h2 { font-size: var(--fs-2xl); color: var(--navy); margin: 0; }
  .pause-timer { font-size: var(--fs-lg); color: var(--text-muted); font-variant-numeric: tabular-nums; }
  .pause-buttons { display: flex; flex-direction: column; gap: 0.7rem; width: 100%; margin-top: 0.5rem; }
  .pause-buttons .btn, .pause-buttons .btn-play, .pause-buttons .btn-secondary { width: 100%; }

  /* Home Game Cards */
  .home-games {
    display: grid; grid-template-columns: repeat(2, 1fr); gap: 0.6rem;
    width: 100%; max-width: 420px;
  }
  .home-game-btn {
    background: var(--card); border: 2px solid var(--border);
    border-radius: 10px; padding: 0.7rem 0.5rem;
    cursor: pointer; transition: all 0.2s;
    display: flex; flex-direction: row; align-items: center; gap: 0.6rem;
    text-align: left;
  }
  .home-game-btn:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: 0 4px 12px rgba(27,42,74,0.1); }
  .home-game-btn .hg-icon { flex-shrink: 0; width: 36px; height: 36px; display: flex; align-items: center; justify-content: center; }
  .home-game-btn .hg-icon svg { width: 30px; height: 30px; fill: url(#icon-grad); }
  .home-game-btn .hg-text { display: flex; flex-direction: column; gap: 0.1rem; min-width: 0; }
  .home-game-btn .hg-title { font-size: var(--fs-base); font-weight: 600; color: var(--navy); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
  .home-game-btn .hg-streak { font-size: var(--fs-xs); color: var(--text-muted); }
  .home-game-btn .hg-streak .fire { color: var(--accent); }
  .home-game-btn.played { border-color: var(--success); }
  .home-game-btn.played .hg-title { color: var(--navy); }
  .hg-done { font-size: var(--fs-xs); color: var(--success); font-weight: 600; }
  .hg-improve { font-size: var(--fs-2xs); color: var(--text-muted); font-weight: 400; }
  .hg-continue { font-size: var(--fs-xs); color: var(--accent); font-weight: 600; }
  /* Mobile active press states */
  .home-game-btn:active { transform: scale(0.97); border-color: var(--accent); }
  .btn:active, .btn-play:active, .btn-ok:active { transform: scale(0.97); }
  .tab-btn:active { opacity: 0.7; }
  /* Daily progress bar */
  .daily-progress-wrap {
    width: 100%; max-width: 420px; margin-bottom: 0.3rem;
  }
  .daily-progress-label {
    font-size: var(--fs-xs); color: var(--text-muted); text-align: center; margin-bottom: 0.25rem;
  }
  .daily-progress-bar {
    width: 100%; height: 6px; background: var(--border); border-radius: 99px; overflow: hidden;
  }
  .daily-progress-fill {
    height: 100%; width: 0; background: linear-gradient(90deg, var(--success), #28a745); border-radius: 99px;
    transition: width 0.6s ease;
  }
  /* Time urgency nudge */
  .time-urgency {
    width: 100%; max-width: 420px; text-align: center;
    font-size: var(--fs-xs); color: var(--accent); font-weight: 500;
  }

  /* Game Choose Screen */
  #screen-choose { gap: 1.5rem; padding: 2rem; justify-content: flex-start; padding-top: 1rem; }
  .game-cards { display: flex; gap: 1.5rem; flex-wrap: wrap; justify-content: center; }
  .game-card {
    width: 260px; background: var(--card);
    border: 2px solid var(--border); border-radius: 10px;
    padding: 1.8rem 1.5rem; text-align: center;
    cursor: pointer; transition: all 0.2s;
    display: flex; flex-direction: column; align-items: center; gap: 0.6rem;
  }
  .game-card:hover { border-color: var(--accent); transform: translateY(-3px); box-shadow: 0 4px 12px rgba(27,42,74,0.1); }
  .game-card .card-icon { font-size: 2.8rem; display: flex; align-items: center; justify-content: center; }
  .game-card .card-icon svg { width: 42px; height: 42px; fill: url(#icon-grad); }
  .game-card .card-title { font-size: var(--fs-lg); font-weight: 600; color: var(--navy); }
  .game-card .card-desc { font-size: var(--fs-sm); color: var(--text-muted); line-height: 1.4; }

  /* Quiz Screen */
  #screen-quiz { padding: 1.5rem; gap: 1rem; }
  .quiz-header {
    width: 100%; display: flex; justify-content: space-between;
    align-items: center; padding: 0.7rem 1.2rem;
    background: var(--navy); color: #fff; border-radius: 8px;
    max-width: 700px; flex-wrap: wrap; gap: 0.2rem;
  }
  .quiz-progress { font-size: var(--fs-md); font-weight: bold; }
  .quiz-timer { font-size: var(--fs-md); font-variant-numeric: tabular-nums; }
  .quiz-card {
    width: 100%; max-width: 700px; background: var(--card);
    border: 1px solid var(--border); border-radius: 10px;
    padding: 2rem; display: flex; flex-direction: column; gap: 1.2rem;
  }
  .quiz-question {
    font-size: clamp(1rem, 2.5vw, 1.25rem); color: var(--navy);
    line-height: 1.5; font-weight: 500;
  }
  .quiz-answers { display: flex; flex-direction: column; gap: 0.6rem; }
  .quiz-answer {
    padding: 0.9rem 1.2rem; border: 2px solid var(--border);
    border-radius: 8px; background: #fff; cursor: pointer;
    font-size: var(--fs-md); text-align: left;
    color: var(--text); transition: all 0.15s; line-height: 1.4;
  }
  .quiz-answer:hover { border-color: var(--navy); background: #f0f4ff; }
  .quiz-answer.selected { border-color: var(--accent); background: #fff5ee; }
  .quiz-answer.correct { border-color: var(--success); background: #eaffea; }
  .quiz-answer.wrong { border-color: var(--error); background: #fff0f0; }
  .quiz-answer[disabled] { cursor: default; opacity: 0.85; }
  .quiz-answer[disabled]:hover { background: inherit; border-color: inherit; }
  .quiz-explain {
    font-size: var(--fs-base); color: var(--text-muted); line-height: 1.5;
    padding: 0.8rem; background: rgba(27,42,74,0.03); border-radius: 6px;
    display: none;
  }
  .quiz-explain.visible { display: block; }
  .quiz-next-row { display: flex; justify-content: flex-end; }
  .quiz-next {
    background: var(--accent); color: #fff; border: none;
    padding: 0.7rem 2rem; font-size: var(--fs-md); cursor: pointer;
    border-radius: 6px; transition: all 0.2s;
    display: none;
  }
  .quiz-next.visible { display: inline-block; }
  .quiz-next:hover { background: var(--accent-hover); }

  /* Quiz Result Screen */
  #screen-quiz-result { padding: 2rem; gap: 1rem; }
  .quiz-result-icon { font-size: 4rem; animation: resultPop 0.5s ease; }
  @keyframes resultPop {
    0% { transform: scale(0); opacity: 0; }
    50% { transform: scale(1.3); }
    100% { transform: scale(1); opacity: 1; }
  }
  .quiz-result-text {
    font-size: clamp(1.2rem, 3vw, 1.8rem); color: var(--navy); font-weight: 600; text-align: center;
  }
  .quiz-result-detail {
    font-size: var(--fs-md); color: var(--text-muted); text-align: center; line-height: 1.5;
  }
  /* Puzzle result screen */
  #screen-puzzle-result { padding: 1.5rem; gap: 0.6rem; overflow-y: auto; justify-content: flex-start; padding-top: 1.5rem; }

  /* Shared Puzzle Styles */
  #screen-puzzle { padding: 0; justify-content: flex-start; }
  .puzzle-container {
    width: 100%; max-width: 420px; display: flex; flex-direction: column;
    align-items: center; gap: 0.8rem; padding: 0.8rem; flex: 1;
    overflow: visible;
  }
  .puzzle-grid {
    display: grid; gap: 1px; background: var(--navy); border: 2px solid var(--navy);
    border-radius: 6px; width: calc(100% - 24px); max-width: 348px;
    position: relative; margin: 12px auto;
    overflow: visible;
  }
  .puzzle-grid::before {
    content: ''; position: absolute; inset: 0; z-index: 0; pointer-events: none;
    opacity: 0.03;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='60' height='60'%3E%3Ctext x='30' y='35' text-anchor='middle' font-size='24' fill='%231b2a4a'%3E⊗%3C/text%3E%3C/svg%3E");
  }
  .puzzle-cell {
    background: var(--card); display: flex; align-items: center; justify-content: center;
    font-size: var(--fs-xl); cursor: pointer; transition: background 0.12s;
    user-select: none; position: relative; z-index: 0; min-height: 0;
    aspect-ratio: 1; box-sizing: border-box;
    overflow: visible;
  }
  .puzzle-cell:hover { background: #f0f4ff; }
  .puzzle-cell:hover .sym-svg { color: var(--accent); }
  .puzzle-cell.selected { background: rgba(250,112,73,0.18); box-shadow: inset 0 0 0 2px var(--accent); }
  .puzzle-cell.selected .sym-svg { color: var(--accent); }
  .puzzle-cell.fixed { color: var(--navy); font-weight: bold; cursor: default; }
  .puzzle-cell.fixed:hover { background: #f5f7fb; }
  .puzzle-cell.fixed:hover .sym-svg { color: var(--navy); }
  .puzzle-cell.memory-card .sym-svg { width: 100%; height: 100%; }
  .puzzle-cell.error { box-shadow: inset 0 0 0 2px var(--error); background: rgba(231,76,60,0.2); }
  .puzzle-cell.error .sym-svg { color: var(--error); }
  .puzzle-cell.error.error-other .sym-svg { color: #fff; }
  .puzzle-cell.correct { animation: correctFlash 1.2s ease; }
  @keyframes correctFlash { 0%,30% { background: rgba(40,167,69,0.25) !important; } 100% { } }
  .puzzle-toolbar {
    display: flex; gap: 0.4rem; flex-wrap: wrap; justify-content: center;
    width: 100%; max-width: 360px;
  }
  .puzzle-tool-btn {
    min-width: 44px; min-height: 44px; padding: 0.4rem 0.7rem;
    background: var(--card); border: 2px solid var(--border); border-radius: 8px;
    font-size: var(--fs-lg); cursor: pointer; transition: all 0.15s;
    display: flex; align-items: center; justify-content: center;
    color: var(--navy); font-weight: 600;
  }
  .puzzle-tool-btn:hover { border-color: var(--navy); background: #f0f4ff; }
  .puzzle-tool-btn.active { border-color: var(--accent); background: rgba(250,112,73,0.1); color: var(--accent); }
  .puzzle-tool-btn.erase { font-size: var(--fs-sm); }
  .puzzle-tool-btn.erase-red { font-size: var(--fs-sm); border-color: var(--error); color: var(--error); }
  .puzzle-tool-btn.erase-red:hover { background: rgba(220,53,69,0.08); }
  /* Queens region colors */
  .region-0 { background: #ffe0b2; } .region-1 { background: #bbdefb; }
  .region-2 { background: #ce93d8; } .region-3 { background: #a5d6a7; }
  .region-4 { background: #f48fb1; } .region-5 { background: #fff176; }
  .region-6 { background: #80deea; } .region-7 { background: #ffab91; }
  .puzzle-cell.queen-placed { color: #000; font-weight: bold; font-size: var(--fs-xl); line-height: 1; overflow: hidden; }
  .puzzle-cell .sym-svg { width: 60%; height: 60%; max-width: 28px; max-height: 28px; }
  .puzzle-cell.fixed .sym-svg { color: var(--navy); }
  .puzzle-cell.queen-placed .sym-svg { color: #000; }
  .puzzle-tool-btn .sym-svg { width: 22px; height: 22px; }
  .btn-hint { min-width: 80px; }
  .btn-hint:disabled { opacity: 0.5; cursor: not-allowed; }
  /* Tango clue markers */
  .tango-clue {
    position: absolute; font-size: 11px; color: var(--navy);
    background: var(--bg); border-radius: 50%; width: 18px; height: 18px;
    display: flex; align-items: center; justify-content: center;
    font-weight: bold; z-index: 10; border: 1.5px solid var(--navy);
    line-height: 1; pointer-events: none;
    font-family: 'Arial', 'Helvetica', sans-serif;
    text-align: center; padding: 0; box-sizing: border-box;
    overflow: visible;
  }
  .tango-clue.clue-eq { font-size: 12px; }
  .tango-clue.clue-x { font-size: 12px; }
  .tango-clue.right { right: -9px; top: 50%; transform: translateY(-50%); }
  .tango-clue.bottom { bottom: -9px; left: 50%; transform: translateX(-50%); }
  .tango-clue.clue-error { color: #fff; background: var(--error); border-color: var(--error); }
  /* Zip path */
  .puzzle-cell.zip-path { background: rgba(250,112,73,0.08); }
  .puzzle-cell.zip-path::after {
    content: ''; position: absolute; width: 10px; height: 10px;
    border-radius: 50%; background: var(--accent); opacity: 0.35;
  }
  .puzzle-cell.zip-num { font-weight: bold; color: var(--navy); font-size: var(--fs-md); z-index: 2; }
  .puzzle-cell.zip-num.zip-path { background: var(--accent); color: #fff; }
  .puzzle-cell.zip-num.zip-path::after { display: none; }
  .puzzle-cell.zip-head { box-shadow: inset 0 0 0 2px var(--accent); background: rgba(250,112,73,0.1); }
  .puzzle-cell.zip-head::after { opacity: 0.6; width: 14px; height: 14px; }
  .zip-line-overlay { position: absolute; inset: 0; z-index: 1; pointer-events: none; }

  /* Trikker Logo */
  .trikker-logo {
    display: flex; align-items: center; justify-content: center; gap: 0.5rem; margin-bottom: 0.1rem;
  }
  .trikker-logo svg { height: 52px; width: auto; }
  .trikker-logo-games {
    font-size: clamp(1.4rem, 3.5vw, 2rem); font-weight: 700; color: var(--navy);
    letter-spacing: 0.04em; text-transform: uppercase;
  }
  .home-subtitle {
    font-size: var(--fs-sm); color: var(--muted); font-style: italic;
    margin: -0.2rem 0 0.3rem; text-align: center;
  }

  /* Post-game actions */
  .postgame-section {
    width: 100%; max-width: 550px; margin-top: 0.5rem;
    display: flex; flex-direction: column; gap: 0.6rem; align-items: center;
  }
  .postgame-next {
    width: 100%; background: var(--card); border: 2px solid var(--border);
    border-radius: 10px; padding: 1rem 1.2rem; cursor: pointer;
    display: flex; align-items: center; gap: 1rem;
    transition: all 0.2s; text-align: left;
    color: var(--text);
  }
  .postgame-next:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: 0 3px 10px rgba(27,42,74,0.08); }
  .postgame-next .pg-icon { font-size: var(--fs-3xl); flex-shrink: 0; }
  .postgame-next .pg-info { display: flex; flex-direction: column; }
  .postgame-next .pg-title { font-weight: 600; color: var(--navy); font-size: var(--fs-base); }
  .postgame-next .pg-desc { font-size: var(--fs-sm); color: var(--text-muted); }
  .postgame-links {
    display: flex; gap: 0.6rem; flex-wrap: wrap; justify-content: center; width: 100%;
  }

  /* Guest nudge card */
  .guest-nudge {
    width: 100%; max-width: 550px;
    background: linear-gradient(135deg, var(--card) 0%, #f0f4ff 100%);
    border: 2px solid var(--accent);
    border-radius: 12px;
    padding: 1rem 1.2rem;
    margin-bottom: 0.8rem;
    text-align: center;
    animation: nudge-fade-in 0.5s ease-out;
  }
  .guest-nudge-icon { font-size: 1.6rem; margin-bottom: 0.3rem; }
  .guest-nudge-msg {
    font-size: var(--fs-sm); color: var(--text);
    margin: 0 0 0.7rem 0; line-height: 1.4;
  }
  .guest-nudge-actions {
    display: flex; gap: 0.5rem; justify-content: center; flex-wrap: wrap;
  }
  .guest-nudge-actions .btn-sm {
    padding: 0.4rem 1.2rem; font-size: var(--fs-sm);
  }
  @keyframes nudge-fade-in {
    from { opacity: 0; transform: translateY(8px); }
    to   { opacity: 1; transform: translateY(0); }
  }

  .near-miss-nudge {
    width: 100%; max-width: 550px; text-align: center;
    font-size: var(--fs-sm); color: var(--accent);
    font-weight: 600; padding: 0.5rem 0; margin-bottom: 0.3rem;
    animation: nudge-fade-in 0.5s ease-out;
  }

  .reset-hint {
    width: 100%; text-align: center;
    font-size: var(--fs-xs); color: var(--text-muted);
    padding: 0.2rem 0; opacity: 0.7;
  }

  /* Share buttons */
  .share-row {
    display: flex; gap: 0.5rem; align-items: center; justify-content: center;
    margin-top: 0.3rem;
  }
  .share-row span { font-size: var(--fs-sm); color: var(--text-muted); }
  .share-btn {
    width: 36px; height: 36px; border-radius: 50%; border: 1px solid var(--border);
    background: #fff; cursor: pointer; display: flex; align-items: center; justify-content: center;
    transition: all 0.2s; font-size: 1rem; color: var(--navy);
  }
  .share-btn:hover, .share-btn:active { border-color: var(--accent); color: var(--accent); transform: scale(1.1); }
  .share-btn svg { width: 18px; height: 18px; fill: currentColor; }

  /* Registration panel (used in profile tab) */
  .home-expand-toggle {
    background: none; border: none; color: var(--accent);
    font-size: var(--fs-sm); cursor: pointer;
    padding: 0.3rem 0; text-decoration: underline;
  }
  .home-expand-toggle:hover { color: var(--accent-hover); }
  .home-register-panel {
    width: 100%; max-width: 420px; background: var(--card);
    border: 1px solid var(--border); border-radius: 10px;
    padding: 1.2rem; display: none; flex-direction: column; gap: 0.7rem;
  }
  .home-register-panel.open { display: flex; }
  .home-register-panel h3 { font-size: var(--fs-md); color: var(--navy); margin: 0; }

  /* Mobile: floating reference thumbnail */
  .ref-thumb {
    display: none; position: absolute; top: 52px; right: 8px;
    z-index: 40; cursor: pointer;
    border: 2px solid var(--accent); border-radius: 8px;
    background: #fff; box-shadow: 0 2px 12px rgba(0,0,0,0.15);
    overflow: hidden; transition: transform 0.15s;
  }
  .ref-thumb:active { transform: scale(0.95); }
  .ref-thumb canvas { display: block; width: 100px; height: 80px; }
  .ref-thumb-label {
    display: block; text-align: center; font-size: var(--fs-2xs);
    color: var(--accent); font-weight: 600; padding: 2px 0;
    background: rgba(250,112,73,0.08);
  }
  /* Mobile: full-screen reference overlay */
  .ref-overlay {
    display: none; position: fixed; top: 0; left: 0; right: 0; bottom: 0;
    z-index: 200; background: rgba(0,0,0,0.92);
    flex-direction: column; align-items: center; justify-content: center;
    padding: 1rem; cursor: pointer;
  }
  .ref-overlay.open { display: flex; }
  .ref-overlay-header {
    display: flex; align-items: center; justify-content: space-between;
    width: 100%; max-width: 500px; padding: 0.5rem 0.2rem; color: #fff;
  }
  .ref-overlay-header span { font-size: var(--fs-md); font-weight: 600; }
  .ref-overlay-close {
    background: none; border: none; color: #fff; font-size: 2rem;
    cursor: pointer; padding: 0.2rem 0.5rem; line-height: 1;
  }
  .ref-overlay canvas {
    max-width: calc(100% - 1rem); max-height: 75vh; background: #fff;
    border-radius: 8px;
  }

  /* Responsive */
  @media (max-width: 900px) {
    .game-area { flex-wrap: wrap; }
    .game-panel { min-width: 45%; }
    .palette {
      flex-direction: row; flex-wrap: wrap;
      width: 100%; min-width: unset;
      border-left: none; border-top: 1px solid var(--border);
      justify-content: center;
      max-height: 110px; overflow-y: auto;
    }
    .pal-btn { width: 58px; height: 48px; }
  }
  @media (max-width: 768px) {
    .game-header { padding: 0.4rem 0.6rem; }
    .details-form { max-width: 100%; }
    .game-cards { flex-direction: column; align-items: center; }
    .game-card { width: 100%; max-width: 320px; }

    /* Schema game: mobile layout */
    .game-area { flex-wrap: nowrap; flex-direction: column; overflow: hidden; }
    .game-divider { display: none; }
    .game-panel { min-width: 100%; width: 100%; flex: 1; overflow: hidden; min-height: 0; }
    .game-panel.mobile-hidden { display: none; }
    .game-panel canvas { max-width: 100%; }
    .panel-label { display: none; }
    .ref-thumb { display: block; }
    #screen-game { position: relative; }

    /* Palette: fixed bottom strip on mobile */
    .palette {
      flex-direction: row; flex-wrap: nowrap;
      width: 100%; min-width: unset;
      border-left: none; border-top: 1px solid var(--border);
      justify-content: flex-start;
      max-height: none; overflow-x: auto; overflow-y: hidden;
      padding: 6px 6px; gap: 4px;
      flex-shrink: 0;
      position: fixed; bottom: 0; left: 0; right: 0;
      z-index: 50;
      background: #fff;
      box-shadow: 0 -2px 8px rgba(0,0,0,0.1);
    }
    .game-area {
      padding-bottom: 68px; /* space for fixed palette */
    }
    .pal-btn {
      width: 54px; height: 52px; flex-shrink: 0;
      min-width: 54px;
    }
    .pal-btn .pal-sym { width: 22px; height: 22px; }
    .pal-btn .pal-lbl { font-size: 0.55rem; }

    /* Quiz: tighter on mobile — use full screen */
    #screen-quiz { padding: 0.8rem; gap: 0.6rem; justify-content: flex-start; overflow-y: auto; -webkit-overflow-scrolling: touch; }
    .quiz-header { padding: 0.5rem 0.8rem; border-radius: 0; max-width: 100%; }
    .quiz-card { padding: 0.8rem; gap: 0.6rem; }
    .quiz-question { font-size: 0.95rem; }
    .quiz-answer { padding: 0.6rem 0.8rem; font-size: 0.9rem; }
    .quiz-explain { padding: 0.6rem; font-size: var(--fs-sm); }
    .quiz-next { padding: 0.6rem 1.5rem; }
    /* Home: optimize vertical space */
    #screen-home { padding: 1rem 1rem 0.5rem; padding-top: 1.5rem; gap: 0.5rem; }
    .trikker-logo svg { height: 36px; }
    .trikker-logo-games { font-size: clamp(1.1rem, 3vw, 1.6rem); }
    .daily-badge { margin-bottom: 0.6rem; padding: 0.2rem 0.8rem; font-size: var(--fs-xs); }
    .home-section-label { margin-top: 0.2rem; }
    /* Home game buttons: ensure icons + text fit */
    .home-game-btn { padding: 0.5rem 0.4rem; gap: 0.4rem; }
    .home-game-btn .hg-icon { width: 28px; height: 28px; }
    .home-game-btn .hg-icon svg { width: 24px; height: 24px; }
    .home-game-btn .hg-title { font-size: var(--fs-sm); }
    .home-games { gap: 0.4rem; }
    /* Welcome card: tighter */
    .home-welcome-card { padding: 0.6rem 0.7rem; gap: 0.4rem; }
    .home-welcome-card .hw-avatar { width: 32px; height: 32px; font-size: var(--fs-sm); }
    .home-welcome-card .hw-name { font-size: var(--fs-sm); }
    .home-welcome-card .hw-medal { max-width: 44px; }
    .home-welcome-card .hw-medal-icon { font-size: 1.1rem; }
    .home-welcome-card .hw-medal span:not(.hw-medal-icon) { display: none; }
    /* Engagement nudges: tighter */
    .streak-warning { padding: 0.3rem 0.8rem; font-size: var(--fs-xs); margin-bottom: 0.3rem; }
    .achievement-nudge { padding: 0.3rem 0.8rem; margin-bottom: 0.3rem; }
    .daily-progress-wrap { margin-bottom: 0.2rem; }
    /* Score/result screens: fullscreen scroll */
    #screen-score, #screen-quiz-result, #screen-puzzle-result { padding: 1rem; padding-top: 0.8rem; gap: 0.6rem; -webkit-overflow-scrolling: touch; }
    .score-title { font-size: var(--fs-lg); }
    .postgame-next { padding: 0.7rem 0.8rem; }
    /* Stats screen tighter */
    #screen-stats { padding: 1rem; padding-top: 0.8rem; gap: 0.6rem; }
    .stats-card { padding: 0.8rem; }
  }
  @media (max-width: 480px) {
    .home-welcome-card .hw-medals { gap: 0.3rem; }
    .home-welcome-card .hw-medal { max-width: 28px; }
    .home-welcome-card .hw-medal span:not(.hw-medal-icon) { display: none; }
    .home-welcome-card .hw-medal-icon { font-size: 1rem; }
  }
  @media (max-width: 360px) {
    .home-game-btn .hg-streak { display: none; }
    .home-welcome-card .hw-medals { display: none; }
  }

  /* ── CSP-safe utility classes (replaces inline style="...") ─────────── */
  /* Visibility: marker for initial hidden state. Replaced by JS at boot
     with an inline display:none (via CSSOM, not a style attribute) so the
     existing `.style.display = ''/'none'` toggle pattern keeps working. */
  .is-hidden { display: none; }
  .is-svg-sprite { position: absolute; }
  /* Layout widths */
  .u-mw-420 { max-width: 420px; }
  .u-mw-480 { max-width: 480px; }
  .u-mw-550 { max-width: 550px; }
  .u-mw-full { max-width: 100%; }
  .u-w-full { width: 100%; }
  /* Flex utilities */
  .u-flex { display: flex; }
  .u-flex-row { display: flex; align-items: center; }
  .u-flex-col { display: flex; flex-direction: column; }
  .u-flex-center { display: flex; align-items: center; justify-content: center; }
  .u-flex-center-v { display: flex; align-items: center; }
  .u-justify-center { justify-content: center; }
  .u-justify-between { justify-content: space-between; }
  .u-justify-start { justify-content: flex-start; }
  .u-items-center { align-items: center; }
  .u-gap-03 { gap: 0.3rem; }
  .u-gap-05 { gap: 0.5rem; }
  .u-gap-06 { gap: 0.6rem; }
  .u-gap-08 { gap: 0.8rem; }
  /* Margin utilities */
  .u-m-0 { margin: 0; }
  .u-mt-02 { margin-top: 0.2rem; }
  .u-mt-03 { margin-top: 0.3rem; }
  .u-mt-04 { margin-top: 0.4rem; }
  .u-mt-05 { margin-top: 0.5rem; }
  .u-mt-08 { margin-top: 0.8rem; }
  .u-my-03 { margin-top: 0.3rem; margin-bottom: 0.3rem; }
  .u-mb-03 { margin-bottom: 0.3rem; }
  .u-mb-05 { margin-bottom: 0.5rem; }
  .u-mb-08 { margin-bottom: 0.8rem; }
  .u-ml-auto { margin-left: auto; }
  .u-mr-2px { margin-right: 2px; }
  /* Text utilities */
  .u-text-center { text-align: center; }
  .u-text-muted { color: var(--text-muted); }
  .u-text-error { color: var(--error); }
  .u-text-accent { color: var(--accent); }
  .u-white { color: #fff; }
  .u-nowrap { white-space: nowrap; }
  .u-font-bold { font-weight: bold; }
  .u-font-semi { font-weight: 600; }
  /* Font size utilities */
  .u-fs-2xs { font-size: var(--fs-2xs); }
  .u-fs-xs  { font-size: var(--fs-xs); }
  .u-fs-sm  { font-size: var(--fs-sm); }
  .u-fs-base { font-size: var(--fs-base); }
  .u-fs-emoji { font-size: 1.5rem; }
  .u-fs-icon-xl { font-size: 2.5rem; }
  .u-fs-em-xs { font-size: 0.75em; }
  .u-fs-em-sm { font-size: 0.8em; }
  /* Cursor / border */
  .u-pointer { cursor: pointer; }
  .u-border-none { border-bottom: none; }
  /* Line height */
  .u-lh-14 { line-height: 1.4; }
  /* Helpers for specific patterns */
  .u-flex-1-160 { flex: 1; max-width: 160px; }
  .u-w-auto { width: auto; }
  .u-w-60 { width: 60px; }
  .u-accent-color { accent-color: var(--accent); }
  /* Screen-reader-only / honeypot */
  .u-honeypot {
    position: absolute; left: -9999px; opacity: 0;
    height: 0; overflow: hidden;
  }
  /* Profile label (non-card row) */
  .u-lang-label {
    font-size: var(--fs-base); font-weight: 600;
    color: var(--navy); margin: 0;
  }
  .u-radio-row {
    display: flex; align-items: center;
    gap: 0.3rem; cursor: pointer; margin: 0;
  }
  .u-trikker-row {
    display: flex; align-items: center;
    gap: 0.6rem; font-size: 0.9rem; color: var(--text-muted);
  }
  .u-lang-inline-label {
    font-size: 0.9rem; color: var(--text-muted); margin: 0;
  }
  .u-select-inline {
    padding: 0.4rem 0.6rem; border: 1px solid var(--border);
    border-radius: 6px; font-size: var(--fs-base);
    background: var(--card); color: var(--navy);
  }
  .u-captcha-row {
    display: flex; align-items: center; gap: 0.5rem;
  }
  .u-captcha-input { width: 60px; text-align: center; }
  .u-auth-error {
    color: #e74c3c; font-size: var(--fs-sm);
  }
  .u-puzzle-help {
    font-size: var(--fs-xs); color: var(--text-muted);
    text-align: center; max-width: 360px;
    line-height: 1.4; margin-top: 0.2rem;
  }
  /* Shared small avatar circles used in JS-rendered lists */
  .u-avatar-circle {
    width: 28px; height: 28px; border-radius: 50%;
    background: var(--navy); color: #fff;
    display: flex; align-items: center; justify-content: center;
    font-size: 14px; font-weight: bold; flex-shrink: 0;
  }
  /* Scalable avatar circle - size set via CSS variables */
  .u-avatar-scalable {
    border-radius: 50%; color: #fff;
    display: flex; align-items: center; justify-content: center;
    font-weight: bold; flex-shrink: 0;
    width: var(--av-size, 44px); height: var(--av-size, 44px);
    font-size: var(--av-fs, 1rem);
    background: var(--av-bg, var(--navy));
  }
  .u-avatar-scalable svg.sym-svg {
    width: var(--av-sym-size, 24px); height: var(--av-sym-size, 24px);
  }
  /* Queens/memory inline symbol wrapper */
  .u-sym-inline {
    display: inline-block; width: 1.2em; height: 1.2em; vertical-align: middle;
  }
  .u-sym-cell {
    width: 90%; height: 90%;
    display: flex; align-items: center; justify-content: center;
  }
  /* Puzzle toolbar help text */
  .u-toolbar-help {
    color: var(--text-muted); font-size: var(--fs-sm); text-align: center;
  }
  /* Zip undo/reset row */
  .u-zip-tools { display: flex; gap: 0.5rem; justify-content: center; }
  /* Postgame XP header */
  .u-xp-header {
    text-align: center; font-weight: 600; color: var(--accent);
    margin-bottom: 0.3rem; font-size: var(--fs-sm);
  }
  /* Postgame combo row */
  .u-combo-row {
    display: flex; justify-content: space-between; align-items: center;
    margin-top: 0.8rem; gap: 0.5rem;
  }
  /* Postgame hint info */
  .u-hint-info { font-size: 0.75em; color: var(--text-muted); }
  .u-hint-info-big { font-size: 0.75em; color: var(--text-muted); margin-left: auto; white-space: nowrap; }
  /* Achievement group header count */
  .u-ach-group-count { display: flex; align-items: center; gap: 0.3rem; }
  /* Leaderboard XP subscript */
  .u-xp-sub { font-size: 0.75em; color: var(--text-muted); }
  /* Leaderboard flag */
  .u-lb-flag { font-size: 0.8em; margin-right: 2px; }
  /* Memory card back */
  .u-memory-back { color: #fff; font-size: 1.5rem; }
  /* Percentile labels (schema/quiz/puzzle result screens) */
  .u-pctl-label {
    font-size: var(--fs-sm); color: var(--accent);
    font-weight: 600; margin: 0.3rem 0;
  }
  .u-pctl-label--md { margin: 0.4rem 0; }
  /* Hint cooldown label */
  .u-hint-label {
    font-size: var(--fs-xs); color: var(--text-muted); margin-top: 2px;
  }
  /* Lights-out playable cell (set via className, CSP-safe) */
  .u-lightsout-cell {
    aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
    font-size: 1.5rem; cursor: pointer; border-radius: 6px;
    border: 2px solid var(--border); transition: all 0.15s;
  }
  /* Lights-out review cell (non-interactive) */
  .u-lightsout-review {
    aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
    font-size: 1.5rem; border-radius: 6px; border: 2px solid var(--border);
  }
  /* Memory playable cell */
  .u-memory-cell {
    aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
    cursor: pointer; border-radius: 8px;
    border: 2px solid var(--border); transition: all 0.3s; min-height: 60px;
  }
  /* Memory review cell (completed) */
  .u-memory-review {
    aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
    border-radius: 8px; border: 2px solid var(--success);
    background: #d1fae5; min-height: 60px;
  }