/* ═══════════════════════════════════════════════════════
   Williams' √T Theorem — Design System
   Academic brown/cream palette with modern interactions
   ═══════════════════════════════════════════════════════ */

:root {
    --bg-primary: #F5F1E8;
    --bg-secondary: #FFF9F0;
    --bg-card: #FFFFFF;
    --bg-code: #FAF6EF;
    --bg-sidebar: #3B2F20;
    --bg-sidebar-hover: #4E3D2C;

    --text-dark: #2C2416;
    --text-body: #3D3226;
    --text-muted: #7A6E5D;
    --text-light: #F5F1E8;

    --accent-brown: #5C4033;
    --accent-amber: #D4A574;
    --accent-warm: #C67B5C;
    --accent-gold: #B8860B;

    --clr-success: #7A9B76;
    --clr-danger: #C0392B;
    --clr-warning: #C67B5C;
    --clr-info: #5B7FA5;

    --font-heading: 'Source Serif 4', Georgia, 'Times New Roman', serif;
    --font-body: 'Outfit', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', Consolas, monospace;

    --sidebar-width: 280px;
    --transition: 0.3s ease;
    --radius: 12px;
    --radius-sm: 8px;
    --shadow: 0 4px 24px rgba(44, 36, 22, 0.08);
    --shadow-lg: 0 12px 40px rgba(44, 36, 22, 0.12);
}

/* ─── Reset & Base ─── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; font-size: 16px; }

body {
    font-family: var(--font-body);
    background: var(--bg-primary);
    color: var(--text-body);
    line-height: 1.7;
    overflow-x: hidden;
}

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

/* ─── Progress Bar ─── */
.progress-bar {
    position: fixed; top: 0; left: 0; width: 100%; height: 4px;
    background: rgba(92, 64, 51, 0.1); z-index: 1000;
}
.progress-bar__fill {
    height: 100%; width: 0%; background: linear-gradient(90deg, var(--accent-amber), var(--accent-brown));
    transition: width 0.2s ease-out;
}

/* ─── Sidebar ─── */
.sidebar {
    position: fixed; top: 0; left: 0; width: var(--sidebar-width); height: 100vh;
    background: var(--bg-sidebar); color: var(--text-light);
    display: flex; flex-direction: column; z-index: 900;
    padding: 28px 0; overflow-y: auto; transition: transform var(--transition);
}
.sidebar__brand { padding: 0 24px 24px; border-bottom: 1px solid rgba(255,255,255,0.1); }
.sidebar__logo {
    font-family: var(--font-heading); font-size: 1.3rem; font-weight: 700;
    color: var(--accent-amber); text-decoration: none; display: block;
}
.sidebar__subtitle { font-size: 0.75rem; color: rgba(255,255,255,0.5); text-transform: uppercase; letter-spacing: 2px; margin-top: 4px; }
.sidebar__nav { list-style: none; padding: 16px 0; flex: 1; }
.sidebar__link {
    display: flex; align-items: center; gap: 12px; padding: 10px 24px;
    color: rgba(255,255,255,0.6); text-decoration: none; font-size: 0.88rem;
    transition: all var(--transition); border-left: 3px solid transparent;
}
.sidebar__link:hover { color: #fff; background: var(--bg-sidebar-hover); }
.sidebar__link.active { color: var(--accent-amber); border-left-color: var(--accent-amber); background: var(--bg-sidebar-hover); }
.sidebar__dot {
    width: 8px; height: 8px; border-radius: 50%; border: 2px solid currentColor;
    flex-shrink: 0; transition: all var(--transition);
}
.sidebar__link.active .sidebar__dot,
.sidebar__link.visited .sidebar__dot { background: currentColor; }
.sidebar__progress { padding: 16px 24px; border-top: 1px solid rgba(255,255,255,0.1); }
.sidebar__progress span { font-size: 0.8rem; color: rgba(255,255,255,0.5); }
.sidebar__progress-bar { height: 4px; background: rgba(255,255,255,0.1); border-radius: 2px; margin-top: 8px; }
.sidebar__progress-fill { height: 100%; background: var(--accent-amber); border-radius: 2px; width: 0%; transition: width 0.4s ease; }

/* ─── Mobile Header ─── */
.mobile-header {
    display: none; position: fixed; top: 0; left: 0; right: 0; height: 56px;
    background: var(--bg-sidebar); color: var(--text-light); z-index: 950;
    align-items: center; padding: 0 16px; gap: 12px;
}
.mobile-header__toggle {
    background: none; border: none; cursor: pointer; padding: 6px;
    display: flex; flex-direction: column; gap: 4px;
}
.mobile-header__toggle span {
    display: block; width: 22px; height: 2px; background: #fff;
    transition: var(--transition); border-radius: 1px;
}
.mobile-header__title { font-family: var(--font-heading); font-size: 1rem; font-weight: 600; }

/* ─── Content ─── */
.content { margin-left: var(--sidebar-width); min-height: 100vh; }

/* ─── Hero ─── */
.hero {
    text-align: center; padding: 120px 40px 80px;
    background: linear-gradient(180deg, #E8DCC4 0%, var(--bg-primary) 100%);
}
.hero__badge {
    font-size: 0.8rem; text-transform: uppercase; letter-spacing: 3px;
    color: var(--accent-brown); margin-bottom: 24px; font-weight: 600;
}
.hero__title {
    font-family: var(--font-heading); font-size: clamp(2.4rem, 5vw, 3.5rem);
    font-weight: 800; color: var(--text-dark); line-height: 1.15; margin-bottom: 24px;
}
.hero__subtitle {
    font-size: 1.2rem; max-width: 640px; margin: 0 auto 32px;
    color: var(--text-muted); line-height: 1.7;
}
.hero__subtitle em { color: var(--accent-brown); font-style: normal; }
.hero__subtitle strong { color: var(--accent-brown); }
.hero__meta {
    display: flex; justify-content: center; gap: 24px; flex-wrap: wrap;
    margin-bottom: 40px; font-size: 0.9rem; color: var(--text-muted);
}
.hero__cta {
    display: inline-block; padding: 14px 36px; background: var(--accent-brown);
    color: #fff; text-decoration: none; border-radius: var(--radius-sm);
    font-weight: 600; transition: all var(--transition);
}
.hero__cta:hover { background: var(--text-dark); transform: translateY(-2px); box-shadow: var(--shadow-lg); }

/* ─── Sections ─── */
.section { max-width: 900px; margin: 0 auto; padding: 80px 40px; }
.section__header { text-align: center; margin-bottom: 40px; }
.section__number {
    font-family: var(--font-mono); font-size: 0.85rem; color: var(--accent-amber);
    font-weight: 600; display: block; margin-bottom: 8px; letter-spacing: 2px;
}
.section__title {
    font-family: var(--font-heading); font-size: clamp(1.7rem, 3vw, 2.2rem);
    color: var(--text-dark); font-weight: 700; margin-bottom: 12px;
}
.section__difficulty { display: flex; justify-content: center; align-items: center; gap: 6px; font-size: 0.85rem; }
.star { color: #D5C9B2; }
.star.filled { color: var(--accent-amber); }
.section__time { color: var(--text-muted); margin-left: 8px; }
.section__intro {
    font-size: 1.1rem; text-align: center; max-width: 680px; margin: 0 auto 40px;
    color: var(--text-body); line-height: 1.8;
}

/* ─── Demo Boxes ─── */
.demo-box {
    background: var(--bg-card); border: 1px solid rgba(92,64,51,0.12);
    border-radius: var(--radius); padding: 32px; margin-bottom: 40px; box-shadow: var(--shadow);
}
.demo-box__header {
    display: flex; justify-content: space-between; align-items: center;
    margin-bottom: 24px; padding-bottom: 16px; border-bottom: 1px solid rgba(92,64,51,0.08);
}
.demo-box__header h3 { font-family: var(--font-heading); font-size: 1.3rem; color: var(--text-dark); }
.demo-box__badge {
    font-size: 0.7rem; text-transform: uppercase; letter-spacing: 1.5px;
    background: var(--accent-amber); color: #fff; padding: 4px 12px;
    border-radius: 20px; font-weight: 600;
}
.demo-box__instructions { font-size: 0.95rem; color: var(--text-muted); margin-bottom: 20px; }

/* ─── Buttons ─── */
.btn {
    display: inline-flex; align-items: center; gap: 8px; padding: 12px 28px;
    border: none; border-radius: var(--radius-sm); font-family: var(--font-body);
    font-size: 0.95rem; font-weight: 600; cursor: pointer; transition: all var(--transition);
}
.btn--primary { background: var(--accent-brown); color: #fff; }
.btn--primary:hover { background: var(--text-dark); transform: translateY(-1px); box-shadow: var(--shadow); }
.btn--secondary { background: var(--bg-primary); color: var(--accent-brown); border: 1px solid rgba(92,64,51,0.2); }
.btn--secondary:hover { background: var(--accent-brown); color: #fff; }

/* ─── Inputs & Sliders ─── */
.input {
    padding: 10px 16px; border: 1px solid rgba(92,64,51,0.2); border-radius: var(--radius-sm);
    font-family: var(--font-body); font-size: 0.95rem; background: var(--bg-secondary);
    color: var(--text-dark); transition: border-color var(--transition); width: 100%;
}
.input:focus { outline: none; border-color: var(--accent-amber); }
.input--large { font-size: 1.2rem; padding: 12px 20px; font-family: var(--font-mono); }

.slider { -webkit-appearance: none; width: 100%; height: 6px; border-radius: 3px; background: #D5C9B2; outline: none; }
.slider::-webkit-slider-thumb { -webkit-appearance: none; width: 20px; height: 20px; border-radius: 50%; background: var(--accent-brown); cursor: pointer; border: 3px solid #fff; box-shadow: 0 2px 6px rgba(0,0,0,0.15); }
.slider::-moz-range-thumb { width: 20px; height: 20px; border-radius: 50%; background: var(--accent-brown); cursor: pointer; border: 3px solid #fff; }

/* ─── Memory Crisis (Section 1) ─── */
.memory-crisis { display: flex; align-items: center; gap: 24px; justify-content: center; flex-wrap: wrap; margin-bottom: 20px; }
.memory-crisis__panel { text-align: center; flex: 1; min-width: 200px; }
.memory-crisis__panel h4 { font-family: var(--font-heading); margin-bottom: 12px; color: var(--text-dark); }
.memory-crisis__grid {
    display: grid; grid-template-columns: repeat(20, 1fr); gap: 2px;
    max-width: 320px; margin: 0 auto 12px;
}
.memory-crisis__grid--small { grid-template-columns: repeat(10, 1fr); max-width: 160px; }
.memory-crisis__cell {
    width: 100%; aspect-ratio: 1; border-radius: 2px; background: #E8DCC4;
    transition: background 0.15s ease;
}
.memory-crisis__cell.filled { background: var(--accent-brown); }
.memory-crisis__cell.filled-red { background: var(--clr-danger); }
.memory-crisis__vs { font-family: var(--font-heading); font-size: 1.5rem; font-weight: 700; color: var(--text-muted); }
.memory-crisis__count { font-family: var(--font-mono); font-size: 0.85rem; color: var(--text-muted); }
.memory-crisis__verdict { text-align: center; margin: 20px 0; min-height: 50px; }
.memory-crisis__impossible { display: none; font-size: 1.4rem; font-weight: 800; color: var(--clr-danger); animation: shakeIn 0.5s ease; }
.memory-crisis__impossible.show { display: flex; align-items: center; justify-content: center; gap: 12px; }
.memory-crisis__x { font-size: 2rem; }
.memory-crisis__btn { display: block; margin: 0 auto; }
.memory-crisis__reveal { display: none; }
.memory-crisis__reveal.show { display: block; animation: fadeSlideUp 0.6s ease; }
.memory-crisis__possible { background: rgba(122,155,118,0.1); border: 1px solid var(--clr-success); border-radius: var(--radius-sm); padding: 24px; text-align: center; margin-top: 16px; }
.memory-crisis__check { font-size: 2rem; color: var(--clr-success); display: block; margin-bottom: 8px; }
.memory-crisis__subtext { font-size: 0.9rem; color: var(--text-muted); margin-top: 8px; }

/* ─── Insight Box ─── */
.insight-box {
    background: linear-gradient(135deg, rgba(212,165,116,0.1), rgba(212,165,116,0.05));
    border-left: 4px solid var(--accent-amber); padding: 24px 28px;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0; margin: 32px 0;
    display: flex; gap: 16px; align-items: flex-start;
}
.insight-box--breakthrough { border-left-color: var(--clr-success); background: linear-gradient(135deg, rgba(122,155,118,0.1), rgba(122,155,118,0.03)); }
.insight-box__icon { font-size: 1.5rem; flex-shrink: 0; }

/* ─── Comparison Chart (Section 2) ─── */
.comparison-chart__controls { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 20px; }
.comparison-chart__controls label { font-weight: 600; font-size: 0.95rem; white-space: nowrap; }
.comparison-chart__controls .slider { flex: 1; min-width: 200px; }
.comparison-chart__value { font-family: var(--font-mono); font-weight: 600; color: var(--accent-brown); min-width: 80px; }
.comparison-chart__canvas-wrap { width: 100%; overflow-x: auto; margin-bottom: 24px; }
.comparison-chart__canvas-wrap canvas { display: block; max-width: 100%; height: auto; }
.comparison-chart__stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 16px; }

.stat-card { background: var(--bg-secondary); border-radius: var(--radius-sm); padding: 20px; text-align: center; border: 1px solid rgba(92,64,51,0.08); }
.stat-card__label { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 1px; color: var(--text-muted); margin-bottom: 8px; }
.stat-card__value { font-family: var(--font-mono); font-size: 1.5rem; font-weight: 700; color: var(--text-dark); }
.stat-card__sublabel { font-size: 0.8rem; color: var(--text-muted); margin-top: 4px; }
.stat-card--old { border-left: 3px solid var(--clr-danger); }
.stat-card--new { border-left: 3px solid var(--clr-success); }
.stat-card--savings { border-left: 3px solid var(--accent-amber); }
.stat-card--memory { border-left: 3px solid var(--clr-info); }
.stat-card--time { border-left: 3px solid var(--clr-warning); }

/* ─── Analogy Cards (Section 3) ─── */
.analogy-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 20px; margin-bottom: 40px; }
.analogy-card {
    background: var(--bg-card); border: 1px solid rgba(92,64,51,0.1); border-radius: var(--radius);
    padding: 28px; text-align: center; transition: all var(--transition);
}
.analogy-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); }
.analogy-card--highlight { border-color: var(--accent-amber); background: linear-gradient(135deg, #FFF9F0, #FFF5E6); }
.analogy-card__icon { font-size: 2rem; margin-bottom: 12px; }
.analogy-card h4 { font-family: var(--font-heading); margin-bottom: 8px; color: var(--text-dark); }

/* ─── Checkpoint Grid (Section 3) ─── */
.checkpoint-grid {
    display: grid; grid-template-columns: repeat(10, 1fr); gap: 4px; margin-bottom: 20px;
}
.checkpoint-cell {
    aspect-ratio: 1; border-radius: 4px; background: var(--bg-primary);
    border: 1px solid rgba(92,64,51,0.15); cursor: pointer; transition: all 0.2s ease;
    display: flex; align-items: center; justify-content: center;
    font-family: var(--font-mono); font-size: 0.65rem; color: var(--text-muted);
    position: relative;
}
.checkpoint-cell:hover { border-color: var(--accent-amber); background: rgba(212,165,116,0.15); }
.checkpoint-cell.checkpoint { background: var(--accent-amber); color: #fff; border-color: var(--accent-brown); font-weight: 700; }
.checkpoint-cell.optimal { background: var(--clr-success); color: #fff; border-color: #5a7a56; }
.checkpoint-cell.recompute-path { background: rgba(91,127,165,0.3); border-color: var(--clr-info); }
.checkpoint-cell.query-target { background: var(--clr-info); color: #fff; }
.checkpoint-grid__stats { display: flex; gap: 24px; flex-wrap: wrap; margin-bottom: 16px; }
.checkpoint-stat { display: flex; gap: 8px; align-items: center; }
.checkpoint-stat__label { font-size: 0.9rem; color: var(--text-muted); }
.checkpoint-stat__value { font-family: var(--font-mono); font-weight: 700; color: var(--text-dark); }
.checkpoint-grid__actions { display: flex; gap: 12px; flex-wrap: wrap; }
.checkpoint-grid__recompute { margin-top: 16px; padding: 16px; background: var(--bg-secondary); border-radius: var(--radius-sm); display: none; font-size: 0.9rem; }
.checkpoint-grid__recompute.show { display: block; animation: fadeSlideUp 0.3s ease; }

/* ─── Concept Cards ─── */
.concept-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 16px; margin-top: 32px; }
.concept-card {
    display: flex; gap: 16px; align-items: flex-start; background: var(--bg-card);
    padding: 20px; border-radius: var(--radius-sm); border: 1px solid rgba(92,64,51,0.1);
}
.concept-card__num {
    width: 32px; height: 32px; border-radius: 50%; background: var(--accent-brown);
    color: #fff; display: flex; align-items: center; justify-content: center;
    font-weight: 700; font-size: 0.85rem; flex-shrink: 0;
}

/* ─── Edit Distance (Section 4) ─── */
.edit-distance__inputs { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; margin-bottom: 20px; }
.edit-distance__field { flex: 1; min-width: 140px; }
.edit-distance__field label { display: block; font-size: 0.85rem; font-weight: 600; margin-bottom: 4px; color: var(--text-muted); }
.edit-distance__arrow { font-size: 1.5rem; color: var(--text-muted); }
.edit-distance__mode-toggle { display: flex; gap: 0; margin-bottom: 20px; border-radius: var(--radius-sm); overflow: hidden; border: 1px solid rgba(92,64,51,0.15); }
.mode-btn {
    flex: 1; padding: 10px 16px; border: none; background: var(--bg-primary);
    font-family: var(--font-body); font-size: 0.85rem; font-weight: 600;
    cursor: pointer; transition: all var(--transition); color: var(--text-muted);
}
.mode-btn.active { background: var(--accent-brown); color: #fff; }
.edit-distance__table-wrap { overflow-x: auto; margin-bottom: 24px; }
.edit-distance__table { display: inline-block; }
.ed-cell {
    display: inline-flex; align-items: center; justify-content: center;
    width: 44px; height: 44px; font-family: var(--font-mono); font-size: 0.8rem;
    border: 1px solid rgba(92,64,51,0.1); transition: all 0.2s ease;
}
.ed-cell--header { background: var(--accent-brown); color: #fff; font-weight: 700; font-family: var(--font-body); }
.ed-cell--normal { background: var(--bg-secondary); }
.ed-cell--checkpoint { background: rgba(212,165,116,0.3); border-color: var(--accent-amber); }
.ed-cell--hidden { background: var(--bg-primary); color: transparent; border-color: rgba(92,64,51,0.05); }
.ed-cell--path { background: rgba(122,155,118,0.3); border-color: var(--clr-success); }
.edit-distance__stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 16px; }

/* ─── Proof Steps (Section 5) ─── */
.proof-steps { display: flex; flex-direction: column; gap: 32px; margin-bottom: 40px; }
.proof-step {
    background: var(--bg-card); border: 1px solid rgba(92,64,51,0.1);
    border-radius: var(--radius); padding: 28px; position: relative;
}
.proof-step__header { display: flex; align-items: center; gap: 12px; margin-bottom: 12px; }
.proof-step__num {
    font-family: var(--font-mono); font-size: 0.75rem; background: var(--accent-brown);
    color: #fff; padding: 4px 10px; border-radius: 4px; font-weight: 600;
}
.proof-step__header h3 { font-family: var(--font-heading); font-size: 1.15rem; color: var(--text-dark); }
.proof-step__visual {
    min-height: 60px; margin: 16px 0; display: flex; align-items: center;
    gap: 2px; flex-wrap: wrap; padding: 12px; background: var(--bg-primary);
    border-radius: var(--radius-sm);
}
.proof-block {
    height: 28px; border-radius: 3px; display: flex; align-items: center;
    justify-content: center; font-size: 0.6rem; font-family: var(--font-mono);
    color: #fff; flex-shrink: 0;
}
.proof-block--phase { background: var(--accent-brown); flex: 1; min-width: 60px; margin: 2px; }
.proof-block--checkpoint { background: var(--accent-amber); width: 6px; margin: 2px 0; }
.proof-block--recompute { background: var(--clr-info); opacity: 0.6; }
.proof-step__formula {
    font-family: var(--font-mono); font-size: 1.1rem; text-align: center;
    padding: 12px; background: var(--bg-code); border-radius: var(--radius-sm);
    color: var(--accent-brown); font-weight: 600; border: 1px solid rgba(92,64,51,0.08);
    margin: 12px 0;
}
.proof-step__detail { font-size: 0.9rem; color: var(--text-muted); }

/* ─── Scaling Calculator (Section 5) ─── */
.scaling-calc__input { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; flex-wrap: wrap; }
.scaling-calc__input label { font-weight: 600; white-space: nowrap; }
.scaling-table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
.scaling-table th {
    background: var(--accent-brown); color: #fff; padding: 12px 16px;
    text-align: left; font-weight: 600; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.5px;
}
.scaling-table td { padding: 10px 16px; border-bottom: 1px solid rgba(92,64,51,0.08); font-family: var(--font-mono); font-size: 0.85rem; }
.scaling-table tr:nth-child(even) { background: var(--bg-secondary); }
.scaling-table .highlight-row { background: rgba(212,165,116,0.15) !important; font-weight: 600; }

/* ─── Expandable ─── */
.expandable { margin: 24px 0; }
.expandable__header {
    font-family: var(--font-heading); font-size: 1.05rem; font-weight: 600;
    cursor: pointer; padding: 16px 20px; background: var(--bg-secondary);
    border-radius: var(--radius-sm); display: flex; align-items: center; gap: 12px;
    border: 1px solid rgba(92,64,51,0.1); transition: all var(--transition);
}
.expandable__header:hover { background: rgba(212,165,116,0.15); }
.expandable__icon { transition: transform 0.3s ease; font-size: 0.8rem; }
.expandable[open] .expandable__icon { transform: rotate(90deg); }
.expandable__content { padding: 24px 20px; }
.theorem-box {
    background: var(--bg-code); padding: 24px; border-radius: var(--radius-sm);
    border: 1px solid rgba(92,64,51,0.12);
}
.theorem-box h4 { font-family: var(--font-heading); color: var(--text-dark); margin-bottom: 12px; }
.theorem-box__formula {
    font-family: var(--font-mono); font-size: 1rem; text-align: center;
    padding: 16px; margin: 12px 0; background: var(--bg-card); border-radius: var(--radius-sm);
    color: var(--accent-brown); font-weight: 600;
}

/* ─── Tabs (Section 6) ─── */
.tabs__header { display: flex; gap: 0; overflow-x: auto; border-bottom: 2px solid rgba(92,64,51,0.1); margin-bottom: 24px; }
.tabs__tab {
    padding: 12px 20px; border: none; background: none; font-family: var(--font-body);
    font-size: 0.85rem; font-weight: 600; cursor: pointer; color: var(--text-muted);
    white-space: nowrap; border-bottom: 2px solid transparent; margin-bottom: -2px;
    transition: all var(--transition);
}
.tabs__tab:hover { color: var(--accent-brown); }
.tabs__tab.active { color: var(--accent-brown); border-bottom-color: var(--accent-brown); }
.tabs__content { display: none; animation: fadeIn 0.3s ease; }
.tabs__content.active { display: block; }

/* ─── Scenario styles ─── */
.scenario h4 { font-family: var(--font-heading); font-size: 1.2rem; color: var(--text-dark); margin-bottom: 12px; }
.scenario__comparison { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-top: 20px; }
.scenario__item { padding: 20px; border-radius: var(--radius-sm); }
.scenario__item--fail { background: rgba(192,57,43,0.05); border: 1px solid rgba(192,57,43,0.2); }
.scenario__item--pass { background: rgba(122,155,118,0.05); border: 1px solid rgba(122,155,118,0.3); }
.scenario__icon { font-size: 1.5rem; display: block; margin-bottom: 8px; }
.scenario__item--fail .scenario__icon { color: var(--clr-danger); }
.scenario__item--pass .scenario__icon { color: var(--clr-success); }
.scenario__note { font-size: 0.9rem; color: var(--text-muted); margin-top: 16px; font-style: italic; }

/* Memory gauge */
.memory-gauge { position: relative; height: 24px; background: #E8DCC4; border-radius: 12px; margin-top: 12px; overflow: visible; }
.memory-gauge__fill { height: 100%; border-radius: 12px; display: flex; align-items: center; justify-content: center; font-size: 0.7rem; color: #fff; font-weight: 600; }
.memory-gauge__fill--over { background: var(--clr-danger); }
.memory-gauge__fill--ok { background: var(--clr-success); }
.memory-gauge__limit { position: absolute; top: -8px; bottom: -8px; width: 3px; background: var(--text-dark); }
.memory-gauge__limit span { position: absolute; top: -18px; left: 50%; transform: translateX(-50%); font-size: 0.65rem; font-weight: 600; white-space: nowrap; }

/* Cloud calc */
.cloud-calc__row { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; flex-wrap: wrap; }
.cloud-calc__row label { font-weight: 600; min-width: 160px; }
.cloud-calc__row .slider { flex: 1; min-width: 150px; }
.cloud-calc__results { display: grid; gap: 12px; }
.cloud-calc__item { display: flex; justify-content: space-between; padding: 12px 16px; background: var(--bg-primary); border-radius: var(--radius-sm); }
.cloud-calc__item--savings { background: rgba(122,155,118,0.15); }
.cloud-calc__item--delta { background: rgba(212,165,116,0.15); font-weight: 700; }
.cloud-calc__label { font-weight: 500; }
.cloud-calc__cost { font-family: var(--font-mono); font-weight: 700; }

/* Phone cards */
.mobile-comparison { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 20px 0; }
.phone-card { background: var(--bg-primary); border-radius: var(--radius); padding: 20px; border: 1px solid rgba(92,64,51,0.1); }
.phone-card--highlight { border-color: var(--clr-success); background: rgba(122,155,118,0.05); }
.phone-card__header { font-family: var(--font-heading); font-weight: 700; margin-bottom: 16px; text-align: center; }
.phone-card__bar { display: flex; align-items: center; gap: 8px; margin-bottom: 8px; font-size: 0.8rem; }
.phone-card__bar span:first-child { width: 50px; font-weight: 600; }
.phone-card__gauge { flex: 1; height: 10px; background: #E0D6C8; border-radius: 5px; overflow: hidden; }
.phone-card__fill { height: 100%; background: var(--clr-danger); border-radius: 5px; transition: width 1s ease; }
.phone-card__fill--green { background: var(--clr-success); }
.phone-card__fill--yellow { background: var(--accent-amber); }
.phone-card__pct { font-family: var(--font-mono); font-weight: 600; min-width: 35px; text-align: right; }
.phone-card__pct--danger { color: var(--clr-danger); }
.phone-card__verdict { text-align: center; margin-top: 12px; font-weight: 700; font-size: 0.9rem; }
.phone-card__verdict--bad { color: var(--clr-danger); }
.phone-card__verdict--good { color: var(--clr-success); }

/* Science examples */
.science-examples { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 20px; }
.science-example { background: var(--bg-primary); padding: 20px; border-radius: var(--radius-sm); text-align: center; }
.science-example h5 { font-size: 1.1rem; margin-bottom: 8px; }

/* Fibonacci strategies */
.fib-strategies { display: grid; gap: 16px; margin-top: 20px; }
.fib-strategy { padding: 20px; background: var(--bg-primary); border-radius: var(--radius-sm); border: 1px solid rgba(92,64,51,0.08); }
.fib-strategy--optimal { border-color: var(--accent-amber); background: rgba(212,165,116,0.08); }
.fib-strategy h5 { font-family: var(--font-heading); margin-bottom: 8px; }
.fib-strategy__stats { display: flex; gap: 20px; margin-bottom: 8px; }
.fib-stat { font-size: 0.9rem; }
.text-green { color: var(--clr-success); }
.text-red { color: var(--clr-danger); }
.text-amber { color: var(--accent-gold); }

/* ─── Decision Columns (Section 7) ─── */
.decision-columns { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; margin-bottom: 40px; }
.decision-col h3 { display: flex; align-items: center; gap: 8px; font-family: var(--font-heading); margin-bottom: 16px; font-size: 1.1rem; }
.decision-col__icon { font-size: 1.2rem; }
.decision-col--yes h3 { color: var(--clr-success); }
.decision-col--no h3 { color: var(--clr-danger); }
.decision-card {
    background: var(--bg-card); border: 1px solid rgba(92,64,51,0.1); border-radius: var(--radius-sm);
    padding: 16px; margin-bottom: 12px; cursor: default; transition: all var(--transition);
}
.decision-card:hover { transform: translateX(4px); box-shadow: var(--shadow); }
.decision-card h4 { font-size: 0.95rem; margin-bottom: 6px; color: var(--text-dark); }
.decision-card p { font-size: 0.85rem; color: var(--text-muted); }

/* Scenario switcher */
.scenario-switch { display: flex; gap: 0; margin-bottom: 20px; border-radius: var(--radius-sm); overflow: hidden; border: 1px solid rgba(92,64,51,0.15); }
.scenario-switch__btn {
    flex: 1; padding: 10px; border: none; background: var(--bg-primary);
    font-family: var(--font-body); font-size: 0.9rem; font-weight: 600;
    cursor: pointer; transition: all var(--transition); color: var(--text-muted);
}
.scenario-switch__btn.active { background: var(--accent-brown); color: #fff; }
.scenario-detail__verdict {
    display: inline-block; padding: 6px 16px; border-radius: 20px;
    font-weight: 700; font-size: 0.9rem; margin-bottom: 12px;
}
.scenario-detail__verdict--no { background: rgba(192,57,43,0.1); color: var(--clr-danger); }
.scenario-detail__verdict--yes { background: rgba(122,155,118,0.15); color: var(--clr-success); }
.comparison-table { width: 100%; border-collapse: collapse; margin-top: 12px; font-size: 0.85rem; }
.comparison-table th { background: var(--bg-primary); padding: 10px 12px; text-align: left; font-weight: 600; font-size: 0.8rem; }
.comparison-table td { padding: 10px 12px; border-bottom: 1px solid rgba(92,64,51,0.08); }
.comparison-table .highlight-row { background: rgba(212,165,116,0.12); }

/* ─── Lab (Section 8) ─── */
.lab__controls { display: flex; flex-direction: column; gap: 16px; margin-bottom: 24px; }
.lab__control { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.lab__control label { font-weight: 600; min-width: 150px; }
.lab__control .slider { flex: 1; min-width: 150px; }
.lab__optimal { font-size: 0.8rem; color: var(--clr-success); font-weight: 600; }
.lab__visual {
    min-height: 80px; display: flex; flex-wrap: wrap; gap: 3px;
    padding: 16px; background: var(--bg-primary); border-radius: var(--radius-sm);
    margin-bottom: 20px; align-items: center;
}
.lab-cell {
    width: 16px; height: 16px; border-radius: 2px; background: #D5C9B2;
    transition: all 0.2s ease;
}
.lab-cell--checkpoint { background: var(--accent-amber); }
.lab-cell--query { background: var(--clr-info); }
.lab-cell--recompute { background: rgba(91,127,165,0.4); }
.lab__results { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 12px; margin-bottom: 24px; }
.lab__stat { background: var(--bg-secondary); padding: 16px; border-radius: var(--radius-sm); text-align: center; }
.lab__stat-label { font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.5px; color: var(--text-muted); margin-bottom: 4px; }
.lab__stat-value { font-family: var(--font-mono); font-size: 1.3rem; font-weight: 700; color: var(--text-dark); }
.lab__challenges h4 { font-family: var(--font-heading); margin-bottom: 12px; }
.challenge { display: flex; align-items: center; gap: 10px; padding: 8px 0; font-size: 0.9rem; }
.challenge__check { font-size: 1.1rem; }
.challenge.completed .challenge__check { color: var(--clr-success); }

/* ─── Timeline (Section 9) ─── */
.timeline { position: relative; margin: 40px 0; padding-left: 40px; }
.timeline::before { content: ''; position: absolute; left: 12px; top: 0; bottom: 0; width: 2px; background: rgba(92,64,51,0.15); }
.timeline__item { position: relative; margin-bottom: 32px; }
.timeline__item::before {
    content: ''; position: absolute; left: -34px; top: 6px;
    width: 14px; height: 14px; border-radius: 50%;
    background: var(--bg-primary); border: 3px solid var(--accent-brown);
}
.timeline__item--highlight::before { background: var(--accent-amber); border-color: var(--accent-brown); }
.timeline__date { font-family: var(--font-mono); font-size: 0.8rem; color: var(--accent-brown); font-weight: 600; margin-bottom: 4px; }
.timeline__content h4 { font-family: var(--font-heading); margin-bottom: 6px; }

/* ─── Resources Grid ─── */
.resources-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 40px 0; }
.resource-card {
    background: var(--bg-card); border: 1px solid rgba(92,64,51,0.1);
    border-radius: var(--radius); padding: 24px;
}
.resource-card h4 { font-family: var(--font-heading); margin-bottom: 12px; }
.resource-list { list-style: none; }
.resource-list li { padding: 6px 0; border-bottom: 1px solid rgba(92,64,51,0.06); font-size: 0.9rem; }
.resource-list a { color: var(--accent-brown); text-decoration: none; font-weight: 500; }
.resource-list a:hover { text-decoration: underline; }

/* ─── Quiz (Section 9) ─── */
.quiz__progress { margin-bottom: 20px; }
.quiz__progress span { font-size: 0.85rem; color: var(--text-muted); }
.quiz__bar { height: 4px; background: #E8DCC4; border-radius: 2px; margin-top: 8px; }
.quiz__bar-fill { height: 100%; background: var(--accent-amber); border-radius: 2px; transition: width 0.4s ease; }
.quiz__question { font-family: var(--font-heading); font-size: 1.15rem; margin-bottom: 20px; line-height: 1.6; }
.quiz__options { display: flex; flex-direction: column; gap: 10px; margin-bottom: 16px; }
.quiz-option {
    padding: 14px 20px; background: var(--bg-secondary); border: 1px solid rgba(92,64,51,0.12);
    border-radius: var(--radius-sm); cursor: pointer; transition: all var(--transition);
    font-size: 0.95rem;
}
.quiz-option:hover { border-color: var(--accent-amber); background: rgba(212,165,116,0.1); }
.quiz-option.correct { background: rgba(122,155,118,0.2); border-color: var(--clr-success); }
.quiz-option.incorrect { background: rgba(192,57,43,0.1); border-color: var(--clr-danger); }
.quiz-option.disabled { pointer-events: none; }
.quiz__feedback { margin-bottom: 12px; padding: 12px 16px; border-radius: var(--radius-sm); display: none; font-size: 0.9rem; }
.quiz__feedback.show { display: block; animation: fadeIn 0.3s ease; }
.quiz__feedback--correct { background: rgba(122,155,118,0.15); color: #4a6b47; }
.quiz__feedback--incorrect { background: rgba(192,57,43,0.1); color: #8b2020; }
.quiz__score { text-align: center; padding: 32px; }
.quiz__score h3 { font-family: var(--font-heading); font-size: 2rem; margin-bottom: 12px; }

/* ─── Footer ─── */
.footer { background: var(--bg-sidebar); color: var(--text-light); padding: 60px 40px 24px; margin-top: 40px; }
.footer__content { max-width: 900px; margin: 0 auto; display: grid; grid-template-columns: 1fr 1fr; gap: 40px; margin-bottom: 40px; }
.footer__logo { font-family: var(--font-heading); font-size: 1.3rem; color: var(--accent-amber); text-decoration: none; display: block; margin-bottom: 8px; }
.footer__brand p, .footer__links p { font-size: 0.9rem; color: rgba(255,255,255,0.6); line-height: 1.6; }
.footer__links h4 { font-family: var(--font-heading); margin-bottom: 8px; color: var(--accent-amber); }
.footer__links .btn { margin-top: 12px; }
.footer__bottom {
    max-width: 900px; margin: 0 auto; padding-top: 24px; border-top: 1px solid rgba(255,255,255,0.1);
    text-align: center; font-size: 0.8rem; color: rgba(255,255,255,0.4);
}
.footer__credits { margin-top: 4px; }
.footer__credits a { color: var(--accent-amber); text-decoration: none; }

/* ─── Animations ─── */
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
@keyframes fadeSlideUp { from { opacity: 0; transform: translateY(16px); } to { opacity: 1; transform: translateY(0); } }
@keyframes shakeIn { 0% { transform: scale(0.8); opacity: 0; } 50% { transform: scale(1.05); } 100% { transform: scale(1); opacity: 1; } }

.section { opacity: 0; transform: translateY(30px); transition: opacity 0.6s ease, transform 0.6s ease; }
.section.visible { opacity: 1; transform: translateY(0); }

/* ─── Responsive ─── */
@media (max-width: 1024px) {
    .sidebar { transform: translateX(-100%); }
    .sidebar.open { transform: translateX(0); box-shadow: 4px 0 20px rgba(0,0,0,0.3); }
    .mobile-header { display: flex; }
    .content { margin-left: 0; }
    .hero { padding-top: 80px; }
}

@media (max-width: 768px) {
    .section { padding: 60px 20px; }
    .hero { padding: 80px 20px 60px; }
    .comparison-chart__stats { grid-template-columns: 1fr; }
    .analogy-cards { grid-template-columns: 1fr; }
    .scenario__comparison { grid-template-columns: 1fr; }
    .mobile-comparison { grid-template-columns: 1fr; }
    .science-examples { grid-template-columns: 1fr; }
    .decision-columns { grid-template-columns: 1fr; }
    .resources-grid { grid-template-columns: 1fr; }
    .footer__content { grid-template-columns: 1fr; }
    .edit-distance__inputs { flex-direction: column; }
    .edit-distance__arrow { display: none; }
    .demo-box { padding: 20px; }
}

/* ─── Print ─── */
@media print {
    .sidebar, .mobile-header, .progress-bar, .btn, .tabs__header, .slider { display: none !important; }
    .content { margin-left: 0; }
    .section { opacity: 1; transform: none; page-break-inside: avoid; }
    .tabs__content { display: block !important; }
    body { background: #fff; color: #000; }
}