:root {
    --bg-deep: #080b14;
    --bg-surface: #0f1420;
    --bg-card: #151c2c;
    --bg-elevated: #1b2540;
    --border: #243049;
    --border-light: #2d3b58;
    --text-primary: #edf2f7;
    --text-secondary: #8b9dc3;
    --text-muted: #5a6f96;
    --accent: #38bdf8;
    --accent-dim: rgba(56, 189, 248, 0.12);
    --accent-glow: rgba(56, 189, 248, 0.25);
    --success: #34d399;
    --success-dim: rgba(52, 211, 153, 0.12);
    --error: #fb7185;
    --error-dim: rgba(251, 113, 133, 0.12);
    --warning: #fbbf24;
    --purple: #a78bfa;
    --radius: 12px;
    --radius-lg: 20px;
    --radius-sm: 8px;
    --font-display: 'Fraunces', Georgia, serif;
    --font-body: 'Outfit', system-ui, sans-serif;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
}

body {
    font-family: var(--font-body);
    background: var(--bg-deep);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
}

.noise-overlay {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 9999;
    opacity: 0.03;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* Screens */
.screen { display: none; }
.screen.active { display: block; }

.hidden { display: none !important; }

/* ========== LANDING ========== */

.landing-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px 40px;
    border-bottom: 1px solid var(--border);
}

.logo-badge {
    font-family: var(--font-body);
    font-weight: 700;
    font-size: 0.85rem;
    letter-spacing: 0.08em;
    color: var(--accent);
    background: var(--accent-dim);
    padding: 6px 14px;
    border-radius: 6px;
    border: 1px solid rgba(56, 189, 248, 0.2);
}

.landing-nav {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.85rem;
    color: var(--text-muted);
}

.nav-divider { opacity: 0.4; }

/* Hero */
.hero {
    display: grid;
    grid-template-columns: 1fr auto;
    align-items: center;
    max-width: 1100px;
    margin: 0 auto;
    padding: 80px 40px 60px;
    gap: 40px;
}

.hero-eyebrow {
    font-size: 0.8rem;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: 16px;
}

.hero-title {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: clamp(2.4rem, 5vw, 3.6rem);
    line-height: 1.15;
    color: var(--text-primary);
    margin-bottom: 20px;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.05rem;
    color: var(--text-secondary);
    max-width: 480px;
    line-height: 1.7;
    margin-bottom: 32px;
}

.hero-stats {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

.stat-pill {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 100px;
    font-size: 0.85rem;
}

.stat-number {
    font-weight: 700;
    color: var(--accent);
}

.stat-text {
    color: var(--text-secondary);
}

.hero-decoration {
    display: flex;
    align-items: center;
    justify-content: center;
}

.hero-svg {
    width: 300px;
    height: 300px;
    opacity: 0.7;
    animation: floatRotate 30s linear infinite;
}

@keyframes floatRotate {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

/* Chapters Section */
.chapters-section {
    max-width: 1100px;
    margin: 0 auto;
    padding: 20px 40px 80px;
}

.section-title {
    font-family: var(--font-display);
    font-weight: 500;
    font-size: 1.4rem;
    color: var(--text-primary);
    margin-bottom: 28px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
}

.chapter-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 16px;
}

.chapter-card {
    position: relative;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px;
    cursor: pointer;
    transition: var(--transition);
    overflow: hidden;
}

.chapter-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, var(--accent-dim), transparent 60%);
    opacity: 0;
    transition: opacity var(--transition);
}

.chapter-card:hover {
    border-color: var(--accent);
    transform: translateY(-2px);
    box-shadow: 0 8px 32px rgba(56, 189, 248, 0.08);
}

.chapter-card:hover::before { opacity: 1; }

.card-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 14px;
    position: relative;
    z-index: 1;
}

.card-icon {
    width: 42px;
    height: 42px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-dim);
    border-radius: 10px;
    color: var(--accent);
    font-size: 1.2rem;
}

.card-count {
    font-size: 0.78rem;
    font-weight: 500;
    color: var(--text-muted);
    background: var(--bg-elevated);
    padding: 4px 10px;
    border-radius: 100px;
}

.card-title {
    font-weight: 600;
    font-size: 1.05rem;
    color: var(--text-primary);
    margin-bottom: 4px;
    position: relative;
    z-index: 1;
}

.card-subtitle {
    font-size: 0.82rem;
    color: var(--text-muted);
    position: relative;
    z-index: 1;
}

.card-arrow {
    position: absolute;
    right: 24px;
    bottom: 24px;
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent);
    opacity: 0;
    transform: translateX(-8px);
    transition: var(--transition);
}

.chapter-card:hover .card-arrow {
    opacity: 1;
    transform: translateX(0);
}

/* Footer */
.landing-footer {
    text-align: center;
    padding: 32px 40px;
    border-top: 1px solid var(--border);
    color: var(--text-muted);
    font-size: 0.82rem;
}

/* ========== QUIZ ========== */

.quiz-chrome {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 28px;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(12px);
}

.chrome-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    background: none;
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-family: var(--font-body);
    font-size: 0.85rem;
    transition: var(--transition);
}

.chrome-btn:hover {
    color: var(--text-primary);
    border-color: var(--border-light);
    background: var(--bg-card);
}

.chrome-center {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
}

.chrome-chapter {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-primary);
}

.chrome-progress {
    font-size: 0.82rem;
    font-weight: 500;
    color: var(--text-muted);
}

.quiz-progress-bar-wrap {
    height: 3px;
    background: var(--bg-card);
}

.quiz-progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--purple));
    width: 0%;
    transition: width 0.4s ease;
}

.quiz-body {
    max-width: 720px;
    margin: 0 auto;
    padding: 48px 28px 80px;
}

.question-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 36px;
    animation: cardIn 0.35s ease;
}

@keyframes cardIn {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

.question-meta {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 20px;
}

.q-number {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--accent);
    background: var(--accent-dim);
    padding: 4px 10px;
    border-radius: 6px;
}

.q-type {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    background: var(--bg-elevated);
    padding: 4px 10px;
    border-radius: 6px;
}

.q-text {
    font-family: var(--font-display);
    font-weight: 500;
    font-size: 1.25rem;
    line-height: 1.6;
    color: var(--text-primary);
    margin-bottom: 28px;
}

.q-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.option-btn {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 16px 20px;
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    font-family: var(--font-body);
    font-size: 0.95rem;
    color: var(--text-primary);
    transition: var(--transition);
    text-align: left;
    width: 100%;
    line-height: 1.5;
}

.option-btn:hover:not(.locked) {
    border-color: var(--accent);
    background: var(--accent-dim);
}

.option-letter {
    flex-shrink: 0;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    font-weight: 600;
    font-size: 0.82rem;
    background: var(--bg-elevated);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    transition: var(--transition);
}

.option-btn:hover:not(.locked) .option-letter {
    background: var(--accent);
    color: var(--bg-deep);
    border-color: var(--accent);
}

.option-btn.correct {
    border-color: var(--success);
    background: var(--success-dim);
}

.option-btn.correct .option-letter {
    background: var(--success);
    color: var(--bg-deep);
    border-color: var(--success);
}

.option-btn.wrong {
    border-color: var(--error);
    background: var(--error-dim);
}

.option-btn.wrong .option-letter {
    background: var(--error);
    color: var(--bg-deep);
    border-color: var(--error);
}

.option-btn.locked {
    cursor: default;
    opacity: 0.6;
}

.option-btn.correct.locked,
.option-btn.wrong.locked {
    opacity: 1;
}

/* Feedback */
.q-feedback {
    margin-top: 20px;
    padding: 16px 20px;
    border-radius: var(--radius);
    display: flex;
    align-items: flex-start;
    gap: 12px;
    animation: feedbackIn 0.3s ease;
}

@keyframes feedbackIn {
    from { opacity: 0; transform: translateY(-6px); }
    to { opacity: 1; transform: translateY(0); }
}

.q-feedback.correct-feedback {
    background: var(--success-dim);
    border: 1px solid rgba(52, 211, 153, 0.25);
}

.q-feedback.wrong-feedback {
    background: var(--error-dim);
    border: 1px solid rgba(251, 113, 133, 0.25);
}

.feedback-icon {
    flex-shrink: 0;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    font-size: 0.85rem;
}

.correct-feedback .feedback-icon { color: var(--success); }
.wrong-feedback .feedback-icon { color: var(--error); }

.feedback-text {
    font-size: 0.9rem;
    line-height: 1.5;
}

.correct-feedback .feedback-text { color: var(--success); }
.wrong-feedback .feedback-text { color: var(--error); }

/* Quiz Actions */
.quiz-actions {
    display: flex;
    justify-content: flex-end;
    margin-top: 24px;
}

.btn-next {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 14px 28px;
    background: var(--accent);
    color: var(--bg-deep);
    border: none;
    border-radius: var(--radius);
    font-family: var(--font-body);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    animation: fadeUp 0.3s ease;
}

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

.btn-next:hover {
    background: #60cdfa;
    transform: translateY(-1px);
    box-shadow: 0 4px 20px var(--accent-glow);
}

/* ========== RESULTS ========== */

.results-wrap {
    max-width: 560px;
    margin: 0 auto;
    padding: 64px 28px 40px;
    text-align: center;
}

.results-eyebrow {
    font-size: 0.8rem;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: 8px;
}

.results-title {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 1.8rem;
    color: var(--text-primary);
    margin-bottom: 40px;
}

.score-ring-container {
    position: relative;
    width: 200px;
    height: 200px;
    margin: 0 auto 36px;
}

.score-ring {
    width: 100%;
    height: 100%;
    transform: rotate(0deg);
}

#score-circle {
    transition: stroke-dashoffset 1.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.score-center {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.score-percent {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 2.8rem;
    color: var(--text-primary);
    line-height: 1;
}

.score-label {
    font-size: 0.82rem;
    color: var(--text-muted);
    margin-top: 4px;
}

.results-stats {
    display: flex;
    justify-content: center;
    gap: 32px;
    margin-bottom: 28px;
}

.rstat {
    text-align: center;
}

.rstat-value {
    display: block;
    font-size: 1.8rem;
    font-weight: 700;
    line-height: 1;
    margin-bottom: 4px;
}

.rstat.correct .rstat-value { color: var(--success); }
.rstat.wrong .rstat-value { color: var(--error); }
.rstat.total .rstat-value { color: var(--accent); }

.rstat-label {
    font-size: 0.78rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.score-message {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 36px;
    line-height: 1.6;
}

.results-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

.results-actions button {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 22px;
    border-radius: var(--radius);
    font-family: var(--font-body);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid var(--border);
}

.btn-review {
    background: var(--accent-dim);
    color: var(--accent);
    border-color: rgba(56, 189, 248, 0.2) !important;
}

.btn-review:hover {
    background: rgba(56, 189, 248, 0.2);
}

.btn-retry {
    background: var(--success-dim);
    color: var(--success);
    border-color: rgba(52, 211, 153, 0.2) !important;
}

.btn-retry:hover {
    background: rgba(52, 211, 153, 0.2);
}

.btn-home {
    background: var(--bg-card);
    color: var(--text-secondary);
}

.btn-home:hover {
    background: var(--bg-elevated);
    color: var(--text-primary);
}

/* Review Section */
.review-section {
    max-width: 720px;
    margin: 0 auto;
    padding: 20px 28px 80px;
}

.review-title {
    font-family: var(--font-display);
    font-weight: 500;
    font-size: 1.3rem;
    color: var(--text-primary);
    margin-bottom: 24px;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--border);
}

.review-list {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.review-item {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 24px;
    border-left: 3px solid var(--success);
}

.review-item.wrong-answer {
    border-left-color: var(--error);
}

.review-q-head {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 12px;
}

.review-q-num {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 3px 8px;
    border-radius: 5px;
}

.review-item:not(.wrong-answer) .review-q-num {
    background: var(--success-dim);
    color: var(--success);
}

.review-item.wrong-answer .review-q-num {
    background: var(--error-dim);
    color: var(--error);
}

.review-q-status {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.review-q-text {
    font-size: 0.95rem;
    color: var(--text-primary);
    margin-bottom: 14px;
    line-height: 1.6;
}

.review-answers {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.review-opt {
    font-size: 0.85rem;
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
}

.review-opt.was-correct {
    background: var(--success-dim);
    color: var(--success);
    font-weight: 500;
}

.review-opt.was-wrong {
    background: var(--error-dim);
    color: var(--error);
    text-decoration: line-through;
    text-decoration-color: rgba(251, 113, 133, 0.4);
}

.review-explanation {
    margin-top: 10px;
    padding: 10px 14px;
    background: var(--bg-elevated);
    border-radius: var(--radius-sm);
    font-size: 0.82rem;
    color: var(--text-secondary);
    line-height: 1.5;
    font-style: italic;
}

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

@media (max-width: 768px) {
    .hero {
        grid-template-columns: 1fr;
        padding: 48px 20px 40px;
        text-align: center;
    }

    .hero-subtitle { margin: 0 auto 32px; }
    .hero-stats { justify-content: center; }
    .hero-decoration { display: none; }

    .landing-header {
        padding: 16px 20px;
    }

    .landing-nav { display: none; }

    .chapters-section { padding: 20px 20px 60px; }
    .chapter-grid { grid-template-columns: 1fr; }

    .quiz-chrome { padding: 12px 16px; }
    .chrome-center { display: none; }
    .quiz-body { padding: 28px 16px 60px; }

    .question-card { padding: 24px 20px; }
    .q-text { font-size: 1.1rem; }

    .results-wrap { padding: 40px 20px 32px; }
    .results-stats { gap: 20px; }
    .results-actions { flex-direction: column; }
    .results-actions button { justify-content: center; }

    .review-section { padding: 16px 16px 60px; }
}

@media (max-width: 380px) {
    .stat-pill { padding: 6px 12px; font-size: 0.78rem; }
    .option-btn { padding: 14px 16px; font-size: 0.88rem; }
    .option-letter { width: 28px; height: 28px; font-size: 0.75rem; }
}

/* ========== SCROLLBAR ========== */

::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-deep); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--border-light); }