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

:root {
    --bg: #0f172a;
    --surface: #1e293b;
    --surface-2: #334155;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --correct: #22c55e;
    --wrong: #ef4444;
    --radius: 12px;
    --transition: 0.2s ease;
}

@media (prefers-color-scheme: light) {
    :root {
        --bg: #f1f5f9;
        --surface: #ffffff;
        --surface-2: #e2e8f0;
        --text: #0f172a;
        --text-muted: #64748b;
        --accent: #6366f1;
        --accent-hover: #4f46e5;
        --correct: #16a34a;
        --wrong: #dc2626;
    }
}

:root[data-theme="dark"] {
    --bg: #0f172a;
    --surface: #1e293b;
    --surface-2: #334155;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --correct: #22c55e;
    --wrong: #ef4444;
}

:root[data-theme="light"] {
    --bg: #f1f5f9;
    --surface: #ffffff;
    --surface-2: #e2e8f0;
    --text: #0f172a;
    --text-muted: #64748b;
    --accent: #6366f1;
    --accent-hover: #4f46e5;
    --correct: #16a34a;
    --wrong: #dc2626;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}

.quiz-wrapper {
    width: 100%;
    max-width: 680px;
}

/* Header */
.quiz-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1.5rem;
}

.quiz-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--accent-hover);
    letter-spacing: 0.05em;
    text-transform: uppercase;
}

.quiz-header-right {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.quiz-counter {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.theme-toggle {
    background: var(--surface);
    border: 1px solid var(--surface-2);
    color: var(--text-muted);
    border-radius: 8px;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: color var(--transition), border-color var(--transition), background var(--transition);
    flex-shrink: 0;
}

.theme-toggle:hover {
    color: var(--text);
    border-color: var(--accent);
}

/* Progress bar */
.progress-bar {
    height: 6px;
    background: var(--surface-2);
    border-radius: 99px;
    margin-bottom: 2rem;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent);
    border-radius: 99px;
    transition: width 0.4s ease;
}

/* Question card */
.question-card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 2rem;
    margin-bottom: 1.5rem;
    border: 1px solid var(--surface-2);
}

.question-note {
    display: inline-block;
    background: color-mix(in srgb, var(--accent) 12%, var(--surface));
    color: var(--accent-hover);
    border: 1px solid color-mix(in srgb, var(--accent) 30%, var(--surface));
    border-radius: 99px;
    padding: 0.2rem 0.75rem;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 0.9rem;
}

.question-text {
    font-size: 1.3rem;
    font-weight: 600;
    line-height: 1.5;
    color: var(--text);
}

/* Answer buttons */
.answers-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
}

@media (max-width: 480px) {
    .answers-grid {
        grid-template-columns: 1fr;
    }

    .question-text {
        font-size: 1.1rem;
    }
}

.answer-btn {
    background: var(--surface);
    border: 2px solid var(--surface-2);
    color: var(--text);
    border-radius: var(--radius);
    padding: 1rem 1.25rem;
    font-size: 1rem;
    font-family: inherit;
    cursor: pointer;
    text-align: left;
    line-height: 1.4;
    transition: border-color var(--transition), background var(--transition), transform var(--transition);
    position: relative;
    overflow: hidden;
}

.answer-btn:hover:not(:disabled) {
    border-color: var(--accent);
    background: color-mix(in srgb, var(--accent) 10%, var(--surface));
    transform: translateY(-1px);
}

.answer-btn:disabled {
    cursor: default;
}

.answer-btn.correct {
    background: color-mix(in srgb, var(--correct) 20%, var(--surface));
    border-color: var(--correct);
    color: #fff;
}

.answer-btn.wrong {
    background: color-mix(in srgb, var(--wrong) 20%, var(--surface));
    border-color: var(--wrong);
    color: #fff;
}

.answer-btn.correct::after,
.answer-btn.wrong::after {
    content: attr(data-icon);
    position: absolute;
    right: 1rem;
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.1rem;
}

/* Results screen */
.results-card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 2.5rem 2rem;
    text-align: center;
    border: 1px solid var(--surface-2);
}

.results-title {
    font-size: 1.6rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.results-subtitle {
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.score-ring {
    width: 140px;
    height: 140px;
    margin: 0 auto 2rem;
    position: relative;
}

.score-ring svg {
    width: 100%;
    height: 100%;
    transform: rotate(-90deg);
}

.score-ring .ring-bg {
    fill: none;
    stroke: var(--surface-2);
    stroke-width: 10;
}

.score-ring .ring-fill {
    fill: none;
    stroke: var(--accent);
    stroke-width: 10;
    stroke-linecap: round;
    transition: stroke-dashoffset 0.8s ease;
}

.score-label {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--text);
}

.results-stats {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 2rem;
}

.stat {
    text-align: center;
}

.stat-value {
    font-size: 1.8rem;
    font-weight: 700;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 0.25rem;
}

.stat.correct .stat-value { color: var(--correct); }
.stat.wrong .stat-value { color: var(--wrong); }

.restart-btn {
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: var(--radius);
    padding: 0.85rem 2.5rem;
    font-size: 1rem;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    transition: background var(--transition), transform var(--transition);
}

.restart-btn:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

/* Quiz set selection */
.select-prompt {
    color: var(--text-muted);
    margin-bottom: 1.25rem;
    font-size: 0.95rem;
}

.toggle-group {
    display: flex;
    gap: 0.6rem;
    flex-wrap: wrap;
    margin-bottom: 1.25rem;
}

.toggle-btn {
    background: var(--surface);
    border: 2px solid var(--surface-2);
    color: var(--text-muted);
    border-radius: 99px;
    padding: 0.4rem 1rem;
    font-size: 0.85rem;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    transition: color var(--transition), border-color var(--transition), background var(--transition);
}

.toggle-btn:hover {
    border-color: var(--accent);
    color: var(--text);
}

.toggle-btn.active {
    background: color-mix(in srgb, var(--accent) 15%, var(--surface));
    border-color: var(--accent);
    color: var(--accent-hover);
}

.select-grid {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.select-group-title {
    font-size: 0.8rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-muted);
    margin-bottom: 0.6rem;
}

.select-group-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
}

@media (max-width: 480px) {
    .select-group-grid {
        grid-template-columns: 1fr;
    }
}

.select-card {
    background: var(--surface);
    border: 2px solid var(--surface-2);
    color: var(--text);
    border-radius: var(--radius);
    padding: 1.5rem 1.25rem;
    font-size: 1.05rem;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    text-align: left;
    transition: border-color var(--transition), background var(--transition), transform var(--transition);
}

.select-card:hover {
    border-color: var(--accent);
    background: color-mix(in srgb, var(--accent) 10%, var(--surface));
    transform: translateY(-1px);
}

/* Results actions */
.results-actions {
    display: flex;
    gap: 0.75rem;
    justify-content: center;
    flex-wrap: wrap;
}

.select-btn {
    background: transparent;
    color: var(--text-muted);
    border: 2px solid var(--surface-2);
    border-radius: var(--radius);
    padding: 0.85rem 2rem;
    font-size: 1rem;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    transition: color var(--transition), border-color var(--transition);
}

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

/* Loading / error states */
.status-message {
    text-align: center;
    color: var(--text-muted);
    padding: 3rem;
    font-size: 1.1rem;
}

.hidden {
    display: none;
}