:root {
    --bg-primary: #0a0e1a;
    --bg-secondary: #121829;
    --bg-glass: rgba(255, 255, 255, 0.04);
    --accent: #6366f1;
    --accent-glow: rgba(99, 102, 241, 0.45);
    --accent-2: #8b5cf6;
    --correct: #10b981;
    --correct-soft: rgba(16, 185, 129, 0.15);
    --wrong: #ef4444;
    --wrong-soft: rgba(239, 68, 68, 0.15);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-tertiary: #cbd5e1;
    --border: rgba(255, 255, 255, 0.08);
    --border-strong: rgba(255, 255, 255, 0.15);
    --radius: 18px;
    --shadow: 0 20px 60px -15px rgba(0, 0, 0, 0.6);
    --option-bg: rgba(255, 255, 255, 0.03);
}

[data-theme="light"] {
    --bg-primary: #eef1f6;
    --bg-secondary: #ffffff;
    --bg-glass: rgba(255, 255, 255, 0.8);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #1e293b;
    --border: rgba(0, 0, 0, 0.1);
    --border-strong: rgba(0, 0, 0, 0.18);
    --shadow: 0 20px 60px -15px rgba(99, 102, 241, 0.25);
    --option-bg: rgba(15, 23, 42, 0.03);
}

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

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

body {
    min-height: 100vh;
    font-family: 'DM Sans', system-ui, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 1.5rem 1rem;
    overflow-x: hidden;
    transition: background 0.4s ease, color 0.4s ease;
    position: relative;
}

#bgCanvas {
    position: fixed;
    inset: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    opacity: 0.7;
    pointer-events: none;
}

.quiz-app {
    width: 100%;
    max-width: 620px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: calc(var(--radius) + 8px);
    padding: 2rem;
    box-shadow: var(--shadow);
    backdrop-filter: blur(20px);
    position: relative;
    z-index: 1;
    animation: slideUp 0.6s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(30px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ---------- THEME TOGGLE ---------- */
.theme-toggle {
    position: absolute;
    top: 1.25rem;
    right: 1.25rem;
    width: 44px;
    height: 44px;
    border-radius: 12px;
    background: var(--bg-glass);
    border: 1px solid var(--border);
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    z-index: 5;
}

.theme-toggle:hover {
    border-color: var(--accent);
    box-shadow: 0 0 15px var(--accent-glow);
    transform: translateY(-2px);
}

.theme-toggle svg {
    width: 22px;
    height: 22px;
    transition: all 0.3s ease;
}

[data-theme="light"] .icon-sun { display: none; }
[data-theme="dark"] .icon-moon { display: none; }
.icon-moon { display: none; }
[data-theme="light"] .icon-moon { display: block; }

.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.logo {
    width: 44px;
    height: 44px;
    border-radius: 12px;
    background: linear-gradient(135deg, var(--accent), var(--accent-2));
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: white;
    box-shadow: 0 0 20px var(--accent-glow);
}

.title-block h1 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.4rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

.subtitle {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.header-stats {
    display: flex;
    align-items: center;
    gap: 1rem;
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 0.6rem 1rem;
}

.stat {
    text-align: center;
}

.stat-value {
    display: block;
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--accent);
}

.stat-label {
    font-size: 0.6rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-secondary);
}

.stat-divider {
    width: 1px;
    height: 30px;
    background: var(--border);
}

.quiz-progress {
    position: relative;
    margin-bottom: 2rem;
}

.progress-bar {
    height: 6px;
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    border-radius: 3px;
    width: 10%;
    transition: width 0.5s cubic-bezier(0.16, 1, 0.3, 1);
    box-shadow: 0 0 12px var(--accent-glow);
}

.progress-dots {
    display: flex;
    gap: 4px;
    margin-top: 0.75rem;
    flex-wrap: wrap;
}

.progress-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--bg-glass);
    border: 1px solid var(--border);
    transition: all 0.3s ease;
}

.progress-dot.active {
    background: var(--accent);
    border-color: var(--accent);
    box-shadow: 0 0 8px var(--accent-glow);
}

.progress-dot.correct {
    background: var(--correct);
    border-color: var(--correct);
}

.progress-dot.wrong {
    background: var(--wrong);
    border-color: var(--wrong);
}

.quiz-screen {
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.screen-content {
    text-align: center;
    padding: 1rem 0;
}

.start-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 1.5rem;
    border-radius: 20px;
    background: linear-gradient(135deg, rgba(99,102,241,0.15), rgba(139,92,246,0.08));
    border: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
}

.start-icon svg {
    width: 40px;
    height: 40px;
    color: var(--accent);
}

.screen-content h2 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.6rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
    letter-spacing: -0.02em;
}

.start-desc {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.6;
    max-width: 420px;
    margin: 0 auto 1.5rem;
}

.quiz-meta {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    margin-bottom: 1.75rem;
    flex-wrap: wrap;
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.meta-icon {
    font-size: 1rem;
}

.btn {
    border: none;
    border-radius: var(--radius);
    font-family: 'Space Grotesk', sans-serif;
    font-weight: 600;
    font-size: 0.95rem;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: transform 0.15s ease, box-shadow 0.2s ease, opacity 0.2s ease;
    padding: 0.9rem 1.5rem;
    color: white;
}

.btn svg {
    width: 18px;
    height: 18px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent), var(--accent-2));
    box-shadow: 0 8px 24px -8px var(--accent-glow);
}

.btn-lg {
    padding: 1rem 2rem;
    font-size: 1.05rem;
    margin: 0 auto;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 30px -8px var(--accent-glow);
}

.btn:active {
    transform: translateY(0) scale(0.98);
}

.btn:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;
}

.btn[disabled] {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.btn-secondary {
    background: var(--bg-glass);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

.category-selector {
    margin-top: 1.5rem;
}

#categorySelect {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: 12px;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.9rem;
    padding: 0.7rem 1rem;
    cursor: pointer;
    outline: none;
    transition: border-color 0.2s ease;
}

#categorySelect:focus {
    border-color: var(--accent);
}

.question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.question-category {
    display: inline-block;
    background: linear-gradient(135deg, rgba(99,102,241,0.15), rgba(139,92,246,0.08));
    border: 1px solid var(--border);
    border-radius: 20px;
    padding: 0.3rem 0.9rem;
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    font-weight: 600;
}

.question-number {
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.question-text {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.35rem;
    font-weight: 600;
    line-height: 1.4;
    margin-bottom: 1.5rem;
    letter-spacing: -0.01em;
    color: var(--text-primary);
}

.options-grid {
    display: grid;
    gap: 0.75rem;
}

.option {
    background: var(--option-bg);
    border: 1.5px solid var(--border);
    border-radius: 14px;
    padding: 1rem 1.25rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.2s ease;
    position: relative;
    overflow: hidden;
    color: var(--text-primary);
    text-align: left;
}

.options-grid.general-category .option {
    color: #0f172a !important;
    background: rgba(15, 23, 42, 0.05) !important;
}

.options-grid.general-category .option-letter {
    color: #0f172a !important;
    background: rgba(15, 23, 42, 0.08) !important;
}

.options-grid.general-category .option:hover {
    color: #0f172a !important;
    background: rgba(15, 23, 42, 0.1) !important;
    border-color: var(--accent) !important;
}

.options-grid.general-category .option:hover .option-letter {
    background: var(--accent) !important;
    color: white !important;
}

.options-grid.general-category .option.correct {
    background: var(--correct-soft) !important;
    border-color: var(--correct) !important;
    color: #0f172a !important;
}

.options-grid.general-category .option.correct .option-letter {
    background: var(--correct) !important;
    color: white !important;
}

.options-grid.general-category .option.wrong {
    background: var(--wrong-soft) !important;
    border-color: var(--wrong) !important;
    color: #0f172a !important;
}

.options-grid.general-category .option.wrong .option-letter {
    background: var(--wrong) !important;
    color: white !important;
}

.option-letter {
    width: 32px;
    height: 32px;
    border-radius: 9px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-family: 'Space Grotesk', sans-serif;
    flex-shrink: 0;
    transition: all 0.2s ease;
    color: var(--text-primary);
}

.option:hover {
    border-color: var(--accent);
    transform: translateX(4px);
}

.option:hover .option-letter {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

.option:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.option.selected {
    border-color: var(--accent);
    background: rgba(99, 102, 241, 0.1);
}

.option.correct {
    border-color: var(--correct);
    background: var(--correct-soft);
    animation: pulseCorrect 0.5s ease;
}

.option.correct .option-letter {
    background: var(--correct);
    color: white;
    border-color: var(--correct);
}

.option.wrong {
    border-color: var(--wrong);
    background: var(--wrong-soft);
    animation: shake 0.5s ease;
}

.option.wrong .option-letter {
    background: var(--wrong);
    color: white;
    border-color: var(--wrong);
}

.option.dimmed {
    opacity: 0.5;
}

@keyframes pulseCorrect {
    0% { transform: scale(1); }
    50% { transform: scale(1.02); }
    100% { transform: scale(1); }
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-6px); }
    75% { transform: translateX(6px); }
}

.question-feedback {
    margin-top: 1.5rem;
    padding: 1rem 1.25rem;
    border-radius: 14px;
    border: 1px solid var(--border);
    background: var(--bg-glass);
    animation: fadeIn 0.4s ease;
}

.question-feedback.correct {
    border-color: var(--correct);
    background: var(--correct-soft);
}

.question-feedback.wrong {
    border-color: var(--wrong);
    background: var(--wrong-soft);
}

.feedback-icon {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.feedback-text {
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.question-feedback.correct .feedback-text { color: #34d399; }
.question-feedback.wrong .feedback-text { color: #f87171; }

.feedback-explanation {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

#nextBtn {
    margin: 1.5rem auto 0;
    display: flex;
}

.result-animation {
    font-size: 4rem;
    text-align: center;
    margin-bottom: 1rem;
    animation: popIn 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes popIn {
    0% { opacity: 0; transform: scale(0.3) rotate(-20deg); }
    100% { opacity: 1; transform: scale(1) rotate(0); }
}

.final-score {
    text-align: center;
    margin: 1rem 0;
}

.score-number {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 4rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--accent), var(--accent-2));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.score-max {
    font-size: 1.5rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.score-message {
    text-align: center;
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.result-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.75rem;
    margin-bottom: 2rem;
}

.result-stat {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 1rem 0.5rem;
    text-align: center;
}

.result-stat-value {
    display: block;
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent);
}

.result-stat-label {
    font-size: 0.65rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-secondary);
}

.result-actions {
    display: flex;
    gap: 0.75rem;
}

.result-actions .btn {
    flex: 1;
}

.quiz-footer {
    margin-top: 1.5rem;
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.8rem;
}

@media (max-width: 480px) {
    .quiz-app { padding: 1.5rem; }
    .quiz-header { flex-direction: column; align-items: stretch; }
    .header-stats { justify-content: space-around; }
    .result-stats { grid-template-columns: repeat(2, 1fr); }
    .question-text { font-size: 1.15rem; }
    .screen-content h2 { font-size: 1.35rem; }
    .result-actions { flex-direction: column; }
}