/**
 * @file chessrules.css
 * @description Modern, responsive, theme-aware stylesheet for Marwadi Chess Rules & Academy Guide.
 * Supports light & dark theme modes via [data-theme="dark"], card elevation, glassmorphism, and fluid responsiveness.
 * @project MCHESS Interactive Chess Portal
 */

:root {
    --rules-gold-light: #fbbf24;
    --rules-gold-main: #d4af37;
    --rules-gold-dark: #b45309;
    --rules-gold-glow: rgba(212, 175, 55, 0.2);

    --rules-bg-surface: #ffffff;
    --rules-bg-subtle: #f8fafc;
    --rules-bg-elevated: #ffffff;
    --rules-border: #e2e8f0;
    --rules-border-highlight: rgba(212, 175, 55, 0.4);

    --rules-text-heading: #0f172a;
    --rules-text-body: #334155;
    --rules-text-muted: #64748b;

    --rules-card-shadow: 0 4px 20px -2px rgba(0, 0, 0, 0.05), 0 2px 6px -1px rgba(0, 0, 0, 0.03);
    --rules-card-hover: 0 10px 25px -3px rgba(0, 0, 0, 0.08);

    --rules-primary: #2563eb;
    --rules-primary-hover: #1d4ed8;
    --rules-accent: #0284c7;
    --rules-success: #16a34a;
    --rules-danger: #dc2626;
    --rules-warning: #d97706;
}

[data-theme="dark"] {
    --rules-bg-surface: #151c2c;
    --rules-bg-subtle: #0b0f19;
    --rules-bg-elevated: #1e293b;
    --rules-border: rgba(255, 255, 255, 0.1);
    --rules-border-highlight: rgba(251, 191, 36, 0.45);

    --rules-text-heading: #f8fafc;
    --rules-text-body: #cbd5e1;
    --rules-text-muted: #94a3b8;

    --rules-card-shadow: 0 4px 20px -2px rgba(0, 0, 0, 0.4);
    --rules-card-hover: 0 10px 25px -3px rgba(0, 0, 0, 0.6);

    --rules-primary: #3b82f6;
    --rules-primary-hover: #60a5fa;
    --rules-accent: #38bdf8;
    --rules-success: #22c55e;
    --rules-danger: #ef4444;
    --rules-warning: #f59e0b;
}

/* Global Viewport & Container Guards */
html, body {
    overflow-x: hidden !important;
    max-width: 100vw !important;
}

/* Base Container */
.rules-container {
    max-width: 1240px;
    width: 100%;
    box-sizing: border-box;
    margin: 0 auto;
    padding: 15px 15px 60px;
    color: var(--rules-text-body);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    text-align: left;
    overflow-x: hidden;
}

/* Explicit Touch-Action: Guarantee effortless vertical touch-scrolling over all cards and content */
.rules-container,
.rules-layout,
.rules-main,
.rules-card,
.rules-card *,
.rules-piece-cards-grid,
.rules-piece-card,
.rules-piece-card *,
.rules-piece-card-top,
.rules-piece-symbol-badge,
.rules-piece-card-title,
.rules-piece-card-pts,
.rules-piece-card-desc,
.rules-piece-tags,
.rules-tag,
.rules-piece-tabs,
.rules-piece-tab,
.rules-setup-grid,
.rules-setup-grid *,
.rules-golden-rule-box,
.rules-golden-rule-box *,
.rules-special-card,
.rules-special-card *,
.rules-matrix-wrap,
.rules-matrix-table,
.rules-matrix-mobile-cards,
.rules-matrix-card,
.rules-matrix-card *,
.rules-quiz-box,
.rules-quiz-box *,
.rules-cta-grid,
.rules-cta-card,
.rules-cta-card * {
    touch-action: pan-y !important;
    -webkit-overflow-scrolling: touch;
}

/* Two-Column Responsive Layout */
.rules-layout {
    display: flex;
    gap: 28px;
    align-items: flex-start;
}

.rules-main {
    flex: 1;
    min-width: 0;
}

.rules-sidebar {
    width: 290px;
    flex-shrink: 0;
    position: sticky;
    top: 75px;
}

/* ──────────────────────────────────────────────────────────
   1. HERO SECTION
   ────────────────────────────────────────────────────────── */
.rules-hero {
    position: relative;
    padding: 36px 28px 30px;
    text-align: center;
    background: radial-gradient(circle at 50% 0%, var(--rules-gold-glow) 0%, transparent 70%), var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 16px;
    box-shadow: var(--rules-card-shadow);
    margin-bottom: 24px;
    overflow: hidden;
}

.rules-hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 16px;
    border-radius: 9999px;
    background: rgba(212, 175, 55, 0.12);
    border: 1px solid var(--rules-border-highlight);
    color: var(--rules-gold-dark);
    font-size: 13px;
    font-weight: 700;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    margin-bottom: 14px;
}

[data-theme="dark"] .rules-hero-badge {
    color: var(--rules-gold-light);
    background: rgba(251, 191, 36, 0.15);
}

.rules-hero-title {
    font-size: clamp(24px, 4vw, 36px);
    font-weight: 800;
    color: var(--rules-text-heading);
    line-height: 1.25;
    margin: 0 0 12px 0;
    letter-spacing: -0.5px;
}

.rules-hero-title-highlight {
    background: linear-gradient(135deg, #d4af37, #f59e0b 80%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    display: inline-block;
}

.rules-hero-subtitle {
    font-size: 15.5px;
    line-height: 1.6;
    color: var(--rules-text-muted);
    max-width: 760px;
    margin: 0 auto 20px;
}

/* Hero Quick Stats */
.rules-stats-row {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 12px;
}

.rules-stat-pill {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-radius: 10px;
    font-size: 13px;
    font-weight: 600;
    color: var(--rules-text-heading);
}

.rules-stat-pill i {
    color: var(--rules-gold-main);
}

/* ──────────────────────────────────────────────────────────
   2. CONTENT CARDS
   ────────────────────────────────────────────────────────── */
.rules-card {
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 14px;
    box-shadow: var(--rules-card-shadow);
    padding: 28px 24px;
    margin-bottom: 24px;
    transition: box-shadow 0.25s ease, border-color 0.25s ease;
}

.rules-card:hover {
    box-shadow: var(--rules-card-hover);
}

.rules-section-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 18px;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--rules-border);
}

.rules-section-icon {
    width: 38px;
    height: 38px;
    border-radius: 10px;
    background: rgba(37, 99, 235, 0.1);
    color: var(--rules-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    flex-shrink: 0;
}

[data-theme="dark"] .rules-section-icon {
    background: rgba(59, 130, 246, 0.15);
}

.rules-section-title {
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0;
    line-height: 1.3;
}

.rules-text {
    font-size: 14.5px;
    line-height: 1.65;
    color: var(--rules-text-body);
    margin-bottom: 14px;
}

/* ──────────────────────────────────────────────────────────
   3. BOARD ANATOMY CALLOUTS
   ────────────────────────────────────────────────────────── */
.rules-setup-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin: 20px 0;
}

.rules-golden-rule-box {
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-left: 4px solid var(--rules-gold-main);
    border-radius: 10px;
    padding: 16px;
}

.rules-golden-rule-title {
    font-size: 14.5px;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0 0 6px 0;
    display: flex;
    align-items: center;
    gap: 8px;
}

.rules-golden-rule-title i {
    color: var(--rules-gold-main);
}

.rules-golden-rule-desc {
    font-size: 13.5px;
    line-height: 1.55;
    color: var(--rules-text-muted);
    margin: 0;
}

/* ──────────────────────────────────────────────────────────
   4. INTERACTIVE PIECE MOVEMENT EXPLORER
   ────────────────────────────────────────────────────────── */
.rules-explorer-container {
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-radius: 12px;
    padding: 20px;
    margin: 20px 0;
}

.rules-piece-tabs {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 18px;
    justify-content: center;
}

.rules-piece-tab {
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 8px;
    padding: 8px 14px;
    font-size: 13.5px;
    font-weight: 600;
    color: var(--rules-text-body);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 7px;
    transition: all 0.2s ease;
}

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

.rules-piece-tab.active {
    background: var(--rules-primary);
    color: #ffffff !important;
    border-color: var(--rules-primary);
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.35);
}

.rules-explorer-flex {
    display: flex;
    gap: 24px;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
}

.rules-explorer-board-box {
    width: 320px;
    max-width: 100%;
}

.rules-explorer-board-box .board-container,
.rules-demo-board {
    width: 320px;
    height: 320px;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
    border: 2px solid var(--rules-border);
}

.rules-explorer-info {
    flex: 1;
    min-width: 250px;
    max-width: 420px;
}

.rules-explorer-piece-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 10px;
}

.rules-explorer-piece-name {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--rules-text-heading);
    margin: 0;
}

.rules-explorer-piece-points {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 6px;
    font-size: 12px;
    font-weight: 700;
    background: rgba(212, 175, 55, 0.15);
    color: var(--rules-gold-dark);
    border: 1px solid var(--rules-border-highlight);
}

[data-theme="dark"] .rules-explorer-piece-points {
    color: var(--rules-gold-light);
}

.rules-explorer-summary {
    font-size: 14px;
    line-height: 1.6;
    color: var(--rules-text-body);
    margin-bottom: 14px;
}

.rules-explorer-tips-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.rules-explorer-tips-list li {
    font-size: 13.5px;
    line-height: 1.5;
    color: var(--rules-text-muted);
    margin-bottom: 8px;
    display: flex;
    align-items: flex-start;
    gap: 8px;
}

.rules-explorer-tips-list li i {
    color: var(--rules-success);
    margin-top: 3px;
}

/* Green dot marker for legal moves */
.rules-legal-dot {
    position: absolute;
    width: 28%;
    height: 28%;
    top: 36%;
    left: 36%;
    background: rgba(34, 197, 94, 0.7);
    border-radius: 50%;
    pointer-events: none;
    z-index: 10;
    box-shadow: 0 0 6px rgba(34, 197, 94, 0.8);
}

.rules-capture-ring {
    position: absolute;
    width: 80%;
    height: 80%;
    top: 10%;
    left: 10%;
    border: 4px solid rgba(239, 68, 68, 0.7);
    border-radius: 50%;
    pointer-events: none;
    z-index: 10;
}

/* ──────────────────────────────────────────────────────────
   5. PIECE CARDS GRID
   ────────────────────────────────────────────────────────── */
.rules-piece-cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 16px;
    margin-top: 20px;
}

.rules-piece-card {
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-radius: 12px;
    padding: 18px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.rules-piece-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--rules-card-shadow);
}

.rules-piece-card-top {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
}

.rules-piece-symbol-badge {
    width: 44px;
    height: 44px;
    border-radius: 10px;
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    color: var(--rules-text-heading);
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}

.rules-piece-card-title {
    font-size: 16px;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0 0 2px 0;
}

.rules-piece-card-pts {
    font-size: 12px;
    color: var(--rules-gold-dark);
    font-weight: 600;
}

[data-theme="dark"] .rules-piece-card-pts {
    color: var(--rules-gold-light);
}

.rules-piece-card-desc {
    font-size: 13.5px;
    line-height: 1.55;
    color: var(--rules-text-body);
    margin: 0 0 12px 0;
    flex-grow: 1;
}

.rules-piece-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.rules-tag {
    padding: 3px 8px;
    border-radius: 4px;
    font-size: 11px;
    font-weight: 600;
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    color: var(--rules-text-muted);
}

/* ──────────────────────────────────────────────────────────
   6. SPECIAL MOVES DEMONSTRATION CARDS
   ────────────────────────────────────────────────────────── */
.rules-special-card {
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-radius: 12px;
    padding: 22px;
    margin-bottom: 20px;
}

.rules-special-card-title {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0 0 8px 0;
    display: flex;
    align-items: center;
    gap: 8px;
}

.rules-special-card-title i {
    color: var(--rules-gold-main);
}

.rules-special-flex {
    display: flex;
    gap: 20px;
    align-items: center;
    flex-wrap: wrap;
    margin-top: 14px;
}

.rules-special-board-wrap {
    width: 260px;
    max-width: 100%;
}

.rules-special-board-wrap .board-container {
    width: 260px;
    height: 260px;
    border-radius: 8px;
    border: 1px solid var(--rules-border);
}

.rules-special-controls {
    display: flex;
    gap: 8px;
    margin-top: 10px;
    flex-wrap: wrap;
}

.rules-btn-action {
    background: var(--rules-primary);
    color: #ffffff;
    border: none;
    border-radius: 6px;
    padding: 6px 12px;
    font-size: 12.5px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s ease;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.rules-btn-action:hover {
    background: var(--rules-primary-hover);
}

.rules-btn-secondary {
    background: var(--rules-bg-surface);
    color: var(--rules-text-body);
    border: 1px solid var(--rules-border);
    border-radius: 6px;
    padding: 6px 12px;
    font-size: 12.5px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.rules-btn-secondary:hover {
    border-color: var(--rules-text-muted);
}

.rules-checklist {
    list-style: none;
    padding: 0;
    margin: 12px 0 0;
}

.rules-checklist li {
    font-size: 13.5px;
    line-height: 1.5;
    color: var(--rules-text-body);
    margin-bottom: 8px;
    display: flex;
    align-items: flex-start;
    gap: 8px;
}

.rules-checklist li i {
    color: var(--rules-primary);
    margin-top: 3px;
}

/* ──────────────────────────────────────────────────────────
   7. CHECKMATE VS STALEMATE MATRIX TABLE
   ────────────────────────────────────────────────────────── */
.rules-matrix-wrap {
    overflow-x: auto;
    margin: 20px 0;
    border-radius: 10px;
    border: 1px solid var(--rules-border);
}

.rules-matrix-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--rules-bg-surface);
    font-size: 14px;
}

.rules-matrix-table th {
    background: var(--rules-bg-subtle);
    padding: 12px 16px;
    font-weight: 700;
    color: var(--rules-text-heading);
    border-bottom: 2px solid var(--rules-border);
    text-align: left;
}

.rules-matrix-table td {
    padding: 14px 16px;
    border-bottom: 1px solid var(--rules-border);
    color: var(--rules-text-body);
}

.rules-matrix-table tr:last-child td {
    border-bottom: none;
}

.rules-badge-pill {
    display: inline-block;
    padding: 4px 10px;
    border-radius: 9999px;
    font-size: 12px;
    font-weight: 700;
}

.rules-badge-check {
    background: rgba(37, 99, 235, 0.12);
    color: var(--rules-primary);
    border: 1px solid rgba(37, 99, 235, 0.3);
}

.rules-badge-mate {
    background: rgba(220, 38, 38, 0.12);
    color: var(--rules-danger);
    border: 1px solid rgba(220, 38, 38, 0.3);
}

.rules-badge-draw {
    background: rgba(217, 119, 6, 0.12);
    color: var(--rules-warning);
    border: 1px solid rgba(217, 119, 6, 0.3);
}

/* Mobile-Optimized Matrix Cards (Eliminates horizontal card scroll) */
.rules-matrix-mobile-cards {
    display: none;
}

.rules-matrix-card {
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 10px;
    padding: 14px;
    margin-bottom: 10px;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.04);
}

.rules-matrix-card:last-child {
    margin-bottom: 0;
}

.rules-matrix-card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--rules-border);
}

.rules-matrix-card-title {
    font-size: 15px;
    font-weight: 700;
    color: var(--rules-text-heading);
}

.rules-matrix-card-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    margin-bottom: 10px;
}

.rules-matrix-field {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.rules-matrix-label {
    font-size: 11.5px;
    color: var(--rules-text-muted);
    font-weight: 600;
}

.rules-matrix-outcome {
    font-size: 13px;
    line-height: 1.5;
    color: var(--rules-text-body);
    background: var(--rules-bg-subtle);
    padding: 8px 10px;
    border-radius: 6px;
    border-left: 3px solid var(--rules-primary);
}

/* ──────────────────────────────────────────────────────────
   8. INTERACTIVE QUIZ
   ────────────────────────────────────────────────────────── */
.rules-quiz-box {
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-radius: 12px;
    padding: 22px;
    margin-top: 16px;
}

.rules-quiz-question {
    font-size: 15px;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0 0 12px 0;
}

.rules-quiz-options {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.rules-quiz-opt {
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 8px;
    padding: 10px 14px;
    font-size: 13.5px;
    color: var(--rules-text-body);
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: left;
    display: flex;
    align-items: center;
    gap: 10px;
}

.rules-quiz-opt:hover {
    border-color: var(--rules-primary);
    background: rgba(37, 99, 235, 0.04);
}

.rules-quiz-opt.correct {
    background: rgba(34, 197, 94, 0.15) !important;
    border-color: var(--rules-success) !important;
    color: var(--rules-success) !important;
    font-weight: 700;
}

.rules-quiz-opt.incorrect {
    background: rgba(239, 68, 68, 0.15) !important;
    border-color: var(--rules-danger) !important;
    color: var(--rules-danger) !important;
}

.rules-quiz-feedback {
    display: none;
    margin-top: 10px;
    padding: 10px 14px;
    border-radius: 8px;
    font-size: 13px;
    line-height: 1.5;
}

.rules-quiz-feedback.show {
    display: block;
}

.rules-quiz-feedback.success {
    background: rgba(34, 197, 94, 0.12);
    border: 1px solid rgba(34, 197, 94, 0.3);
    color: var(--rules-success);
}

.rules-quiz-feedback.error {
    background: rgba(239, 68, 68, 0.12);
    border: 1px solid rgba(239, 68, 68, 0.3);
    color: var(--rules-danger);
}

/* ──────────────────────────────────────────────────────────
   9. PRACTICE PATHWAYS CTA CARDS
   ────────────────────────────────────────────────────────── */
.rules-cta-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 16px;
    margin-top: 20px;
}

.rules-cta-card {
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    border-radius: 12px;
    padding: 22px;
    text-align: center;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.rules-cta-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--rules-card-shadow);
}

.rules-cta-icon {
    width: 50px;
    height: 50px;
    border-radius: 12px;
    margin: 0 auto 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
}

.rules-cta-title {
    font-size: 16px;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0 0 6px 0;
}

.rules-cta-desc {
    font-size: 13px;
    color: var(--rules-text-muted);
    line-height: 1.5;
    margin: 0 0 16px 0;
}

.rules-cta-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    padding: 9px 16px;
    border-radius: 8px;
    font-size: 13px;
    font-weight: 700;
    text-decoration: none !important;
    transition: opacity 0.2s ease;
}

.rules-cta-btn:hover {
    opacity: 0.9;
}

/* ──────────────────────────────────────────────────────────
   10. STICKY TABLE OF CONTENTS SIDEBAR
   ────────────────────────────────────────────────────────── */
.rules-toc-card {
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 14px;
    box-shadow: var(--rules-card-shadow);
    padding: 20px;
}

.rules-toc-header {
    font-size: 15px;
    font-weight: 700;
    color: var(--rules-text-heading);
    margin: 0 0 14px 0;
    display: flex;
    align-items: center;
    gap: 8px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--rules-border);
}

.rules-toc-header i {
    color: var(--rules-gold-main);
}

.rules-toc-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.rules-toc-item {
    margin-bottom: 4px;
}

.rules-toc-link {
    display: block;
    padding: 8px 12px;
    border-radius: 8px;
    font-size: 13.5px;
    font-weight: 500;
    color: var(--rules-text-muted);
    text-decoration: none !important;
    transition: all 0.2s ease;
    border-left: 3px solid transparent;
}

.rules-toc-link:hover {
    color: var(--rules-primary);
    background: var(--rules-bg-subtle);
}

.rules-toc-link.active {
    color: var(--rules-primary) !important;
    font-weight: 700;
    background: rgba(37, 99, 235, 0.08);
    border-left-color: var(--rules-primary);
}

[data-theme="dark"] .rules-toc-link.active {
    background: rgba(59, 130, 246, 0.12);
}

/* Mobile Quick-Navigation Pills */
.rules-mobile-nav {
    display: none;
    margin-bottom: 18px;
    background: var(--rules-bg-surface);
    border: 1px solid var(--rules-border);
    border-radius: 12px;
    padding: 12px 14px;
    box-shadow: var(--rules-card-shadow);
}

.rules-mobile-nav-title {
    font-size: 12px;
    font-weight: 700;
    color: var(--rules-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 6px;
}

.rules-mobile-nav-pills {
    display: flex;
    gap: 8px;
    overflow-x: auto;
    padding-bottom: 4px;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
}

.rules-mobile-nav-pills::-webkit-scrollbar {
    display: none;
}

.rules-mobile-nav-pill {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 12px;
    border-radius: 9999px;
    font-size: 12.5px;
    font-weight: 600;
    background: var(--rules-bg-subtle);
    border: 1px solid var(--rules-border);
    color: var(--rules-text-body);
    white-space: nowrap;
    text-decoration: none !important;
    flex-shrink: 0;
    transition: all 0.2s ease;
}

.rules-mobile-nav-pill:hover,
.rules-mobile-nav-pill.active {
    background: var(--rules-primary);
    color: #ffffff !important;
    border-color: var(--rules-primary);
}

/* ──────────────────────────────────────────────────────────
   11. RESPONSIVE DESIGN (TABLET & MOBILE)
   ────────────────────────────────────────────────────────── */
@media (max-width: 991px) {
    .rules-layout {
        flex-direction: column;
        gap: 0;
    }

    /* Hide sticky sidebar on mobile/tablet — top mobile-nav provides instant jump links */
    .rules-sidebar {
        display: none !important;
    }

    .rules-setup-grid {
        grid-template-columns: 1fr;
    }

    .rules-explorer-flex {
        flex-direction: column;
    }

    .rules-explorer-board-box,
    .rules-special-board-wrap {
        width: 100%;
        display: flex;
        justify-content: center;
    }
}

@media (max-width: 768px) {
    .rules-mobile-nav {
        display: block !important;
        margin-bottom: 16px !important;
        padding: 10px 12px !important;
    }

    /* Wrap all navigation pills naturally so all 7 sections fit without horizontal scrolling */
    .rules-mobile-nav-pills {
        display: flex !important;
        flex-wrap: wrap !important;
        gap: 6px !important;
        overflow-x: visible !important;
        padding-bottom: 0 !important;
        justify-content: flex-start !important;
    }

    .rules-mobile-nav-pill {
        padding: 6px 10px !important;
        font-size: 12px !important;
        border-radius: 8px !important;
        white-space: nowrap !important;
        min-height: 36px !important;
        box-sizing: border-box !important;
    }

    .rules-container {
        padding: 10px 8px 40px !important;
        overflow-x: hidden !important;
        max-width: 100% !important;
        box-sizing: border-box !important;
    }

    .rules-hero {
        padding: 20px 12px 16px !important;
        border-radius: 12px !important;
        margin-bottom: 16px !important;
        overflow-x: hidden !important;
    }

    .rules-hero-title {
        font-size: clamp(20px, 5.5vw, 28px) !important;
        margin-bottom: 10px !important;
    }

    .rules-hero-subtitle {
        font-size: 13.5px !important;
        line-height: 1.55 !important;
        margin-bottom: 16px !important;
    }

    /* Hero stats: clean 2x2 grid on mobile screens */
    .rules-stats-row {
        display: grid !important;
        grid-template-columns: repeat(2, 1fr) !important;
        gap: 8px !important;
        width: 100% !important;
    }

    .rules-stat-pill {
        padding: 8px 6px !important;
        font-size: 11.5px !important;
        justify-content: center !important;
        text-align: center !important;
        box-sizing: border-box !important;
    }

    .rules-card {
        padding: 16px 12px !important;
        border-radius: 12px !important;
        margin-bottom: 16px !important;
        overflow-x: hidden !important;
        max-width: 100% !important;
        box-sizing: border-box !important;
    }

    .rules-section-header {
        gap: 10px !important;
        margin-bottom: 14px !important;
        padding-bottom: 10px !important;
    }

    .rules-section-title {
        font-size: 1.15rem !important;
        line-height: 1.35 !important;
    }

    .rules-text {
        font-size: 13.5px !important;
        line-height: 1.6 !important;
    }

    .rules-setup-grid {
        grid-template-columns: 1fr !important;
        gap: 10px !important;
        margin: 14px 0 !important;
    }

    .rules-golden-rule-box {
        padding: 12px 14px !important;
    }

    .rules-piece-cards-grid {
        grid-template-columns: 1fr !important;
        gap: 12px !important;
    }

    .rules-piece-card {
        padding: 14px 12px !important;
        min-width: 0 !important;
        word-break: break-word !important;
        touch-action: pan-y !important;
    }

    .rules-cta-grid {
        grid-template-columns: 1fr !important;
        gap: 12px !important;
    }

    .rules-cta-card {
        padding: 16px 12px !important;
        min-width: 0 !important;
    }

    .rules-cta-btn {
        min-height: 44px !important;
        padding: 10px 16px !important;
        font-size: 13.5px !important;
    }

    .rules-special-card {
        padding: 14px 10px !important;
        border-radius: 10px !important;
        overflow-x: hidden !important;
    }

    .rules-explorer-container {
        padding: 14px 10px !important;
        border-radius: 10px !important;
        overflow-x: hidden !important;
    }

    .rules-special-flex {
        flex-direction: column !important;
        align-items: center !important;
        gap: 14px !important;
    }

    .rules-special-info,
    .rules-explorer-info {
        width: 100% !important;
        min-width: 0 !important;
        max-width: 100% !important;
    }

    /* Sized to comfortably fit 360px phones without horizontal blowout */
    .rules-special-board-wrap,
    .rules-explorer-board-box {
        width: 100% !important;
        max-width: 270px !important;
        margin: 0 auto !important;
        display: flex !important;
        flex-direction: column !important;
        align-items: center !important;
        box-sizing: border-box !important;
    }

    .rules-explorer-board-box .board-container,
    .rules-demo-board,
    .rules-special-board-wrap .board-container,
    #initialSetupBoard,
    #explorerBoard,
    #castleDemoBoard,
    #enPassantDemoBoard {
        width: 270px !important;
        max-width: 100% !important;
        aspect-ratio: 1 / 1 !important;
        height: 270px !important;
        box-sizing: border-box !important;
        margin: 0 auto !important;
    }

    /* Stack demonstration buttons full-width vertically so long labels never wrap poorly */
    .rules-special-controls {
        display: flex !important;
        flex-direction: column !important;
        gap: 8px !important;
        width: 100% !important;
        max-width: 270px !important;
        margin: 12px auto 0 !important;
    }

    .rules-special-controls button {
        width: 100% !important;
        min-height: 44px !important;
        padding: 9px 12px !important;
        font-size: 13px !important;
        justify-content: center !important;
        text-align: center !important;
        white-space: normal !important;
        box-sizing: border-box !important;
    }

    /* Piece tabs: 3 columns grid on mobile to eliminate inner card horizontal scroll */
    .rules-piece-tabs {
        display: grid !important;
        grid-template-columns: repeat(3, 1fr) !important;
        gap: 6px !important;
        overflow-x: visible !important;
        flex-wrap: wrap !important;
        padding-bottom: 0 !important;
        margin-bottom: 14px !important;
        justify-content: stretch !important;
    }

    .rules-piece-tab {
        width: 100% !important;
        padding: 8px 4px !important;
        font-size: 12px !important;
        justify-content: center !important;
        text-align: center !important;
        min-height: 42px !important;
        white-space: normal !important;
        box-sizing: border-box !important;
        flex-shrink: 1 !important;
    }

    /* Hide wide table on mobile and show cards to eliminate horizontal scrollbar */
    .rules-matrix-table {
        display: none !important;
    }

    .rules-matrix-mobile-cards {
        display: flex !important;
        flex-direction: column !important;
        gap: 10px !important;
    }

    .rules-matrix-wrap {
        overflow-x: visible !important;
        border: none !important;
        margin: 12px 0 !important;
        border-radius: 0 !important;
    }

    .rules-quiz-box {
        padding: 16px 12px !important;
        border-radius: 10px !important;
        margin-top: 14px !important;
    }

    .rules-quiz-question {
        font-size: 14px !important;
        line-height: 1.45 !important;
    }

    .rules-quiz-opt {
        padding: 10px 12px !important;
        font-size: 13px !important;
        min-height: 44px !important;
        width: 100% !important;
        box-sizing: border-box !important;
    }
}

/* Extra small devices (<= 380px, e.g. iPhone SE) */
@media (max-width: 380px) {
    .rules-piece-tabs {
        grid-template-columns: repeat(2, 1fr) !important;
    }

    .rules-special-board-wrap,
    .rules-explorer-board-box,
    .rules-explorer-board-box .board-container,
    .rules-demo-board,
    .rules-special-board-wrap .board-container,
    #initialSetupBoard,
    #explorerBoard,
    #castleDemoBoard,
    #enPassantDemoBoard {
        width: 240px !important;
        height: 240px !important;
    }

    .rules-special-controls {
        max-width: 240px !important;
    }
}