/* ============================================
   Data Science Quiz - Style Sheet
   A dark, technical aesthetic with cyan accents
   ============================================ */

@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;500;600;700&family=Source+Sans+3:wght@400;500;600;700&display=swap');

:root {
    /* Color Palette - Dark terminal aesthetic */
    --bg-primary: #0a0e14;
    --bg-secondary: #0f1419;
    --bg-card: #151b23;
    --bg-hover: #1a222d;
    
    --text-primary: #e6e6e6;
    --text-secondary: #8b949e;
    --text-muted: #484f58;
    
    --accent: #00d4aa;
    --accent-dim: #00a888;
    --accent-glow: rgba(0, 212, 170, 0.15);
    
    --correct: #3fb950;
    --correct-bg: rgba(63, 185, 80, 0.15);
    --incorrect: #f85149;
    --incorrect-bg: rgba(248, 81, 73, 0.15);
    
    --border: #21262d;
    --border-light: #30363d;
    
    /* Typography */
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
    --font-sans: 'Source Sans 3', -apple-system, BlinkMacSystemFont, sans-serif;
    
    /* Spacing */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
}

/* Reset & Base */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    
    /* Subtle grid background */
    background-image: 
        linear-gradient(rgba(0, 212, 170, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(0, 212, 170, 0.03) 1px, transparent 1px);
    background-size: 50px 50px;
    background-position: center center;
}

/* Container */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    min-height: 100vh;
}

/* Screen Management */
.screen {
    display: none;
    animation: fadeIn 0.4s ease;
}

.screen.active {
    display: block;
}

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

/* ============================================
   Start Screen
   ============================================ */

.hero {
    text-align: center;
    padding: 1.5rem 0 3rem;
}

.logo {
    font-family: var(--font-mono);
    font-size: 1.5rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

.logo-text {
    color: var(--accent);
    text-shadow: 0 0 30px var(--accent-glow);
}

.channel-link {
    display: inline-flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.5rem 1rem 0.5rem 0.5rem;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 50px;
    text-decoration: none;
    margin-top: 2rem;
    transition: all 0.2s ease;
}

.channel-link:hover {
    border-color: var(--accent);
    background: var(--bg-hover);
    transform: translateY(-2px);
}

.yt-logo {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    background: #ff0000;
    color: white;
    border-radius: 8px;
    font-size: 0.9rem;
}

.channel-name {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-primary);
}

.hero h1 {
    font-family: var(--font-mono);
    font-size: 2.5rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    letter-spacing: -0.02em;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.125rem;
    max-width: 400px;
    margin: 0 auto 2rem;
}

.topic-tags {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.5rem;
    margin-bottom: 2.5rem;
}

.tag {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    padding: 0.375rem 0.75rem;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
}

.info {
    color: var(--text-muted);
    font-size: 0.875rem;
    margin-top: 1.5rem;
}

/* Topic Selector */
.topic-selector {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    margin: 2rem auto;
    max-width: 600px;
    text-align: left;
}

.topic-selector-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.topic-selector-header h3 {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.topic-actions {
    display: flex;
    gap: 0.5rem;
}

.btn-small {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    padding: 0.375rem 0.75rem;
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.15s ease;
}

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

.topic-checkboxes {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.topic-checkbox {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 0.875rem;
    background: var(--bg-secondary);
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.15s ease;
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-secondary);
    user-select: none;
}

.topic-checkbox:hover {
    border-color: var(--border-light);
    background: var(--bg-hover);
}

.topic-checkbox.selected {
    border-color: var(--accent);
    background: var(--accent-glow);
    color: var(--accent);
}

.topic-checkbox input {
    display: none;
}

.topic-checkbox .check-icon {
    width: 14px;
    height: 14px;
    border: 2px solid var(--border-light);
    border-radius: 3px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.15s ease;
    flex-shrink: 0;
}

.topic-checkbox.selected .check-icon {
    background: var(--accent);
    border-color: var(--accent);
}

.topic-checkbox .check-icon::after {
    content: '';
    width: 5px;
    height: 8px;
    border: solid var(--bg-primary);
    border-width: 0 2px 2px 0;
    transform: rotate(45deg) translate(-1px, -1px);
    opacity: 0;
    transition: opacity 0.15s ease;
}

.topic-checkbox.selected .check-icon::after {
    opacity: 1;
}

.topic-count {
    font-size: 0.65rem;
    color: var(--text-muted);
    margin-left: 0.25rem;
}

.topic-checkbox.selected .topic-count {
    color: var(--accent-dim);
}

.topic-warning {
    color: var(--incorrect);
    font-size: 0.8rem;
    margin-top: 0.75rem;
    font-family: var(--font-mono);
}

.topic-warning.hidden {
    display: none;
}

/* Buttons */
.btn-primary {
    font-family: var(--font-mono);
    font-size: 1rem;
    font-weight: 500;
    padding: 0.875rem 2rem;
    background: var(--accent);
    color: var(--bg-primary);
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.2s ease;
    box-shadow: 0 0 20px var(--accent-glow);
}

.btn-primary:hover:not(:disabled) {
    background: var(--accent-dim);
    transform: translateY(-2px);
    box-shadow: 0 4px 30px var(--accent-glow);
}

.btn-primary:disabled {
    opacity: 0.4;
    cursor: not-allowed;
    box-shadow: none;
}

.btn-primary .arrow {
    transition: transform 0.2s ease;
}

.btn-primary:hover:not(:disabled) .arrow {
    transform: translateX(3px);
}

.btn-secondary {
    font-family: var(--font-mono);
    font-size: 1rem;
    font-weight: 500;
    padding: 0.875rem 2rem;
    background: transparent;
    color: var(--accent);
    border: 2px solid var(--accent);
    border-radius: var(--radius-md);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.2s ease;
}

.btn-secondary:hover {
    background: var(--accent-glow);
    transform: translateY(-2px);
}

.btn-back {
    font-family: var(--font-mono);
    font-size: 0.875rem;
    padding: 0.5rem 1rem;
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.15s ease;
}

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

/* ============================================
   Mode Selection Screen
   ============================================ */

.mode-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    margin: 2.5rem 0;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.mode-card {
    background: var(--bg-card);
    border: 2px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 2rem;
    text-align: center;
    transition: all 0.2s ease;
    cursor: pointer;
}

.mode-card:hover {
    border-color: var(--accent);
    transform: translateY(-4px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.3);
}

.mode-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.mode-card h3 {
    font-family: var(--font-mono);
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.beta-badge {
    font-size: 0.6rem;
    padding: 0.2rem 0.5rem;
    background: linear-gradient(135deg, #ff6b35, #f7931e);
    color: #fff;
    border-radius: 4px;
    font-weight: 600;
    letter-spacing: 0.05em;
}

.course-header h2 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.course-beta-note {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 1.5rem;
    padding: 0.75rem 1rem;
    background: rgba(247, 147, 30, 0.1);
    border: 1px solid rgba(247, 147, 30, 0.3);
    border-radius: var(--radius-sm);
}

.mode-card p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

.mode-progress, .mode-stats {
    margin-bottom: 1.5rem;
    padding: 0.75rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
}

.progress-text, .stats-text {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-muted);
}

.progress-bar-mini {
    height: 4px;
    background: var(--bg-primary);
    border-radius: 2px;
    margin-top: 0.5rem;
    overflow: hidden;
}

.progress-fill-mini {
    height: 100%;
    background: var(--accent);
    border-radius: 2px;
    transition: width 0.3s ease;
}

/* ============================================
   Course Overview Screen
   ============================================ */

.course-header, .practice-header, .lesson-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 2rem;
}

.course-header h2, .practice-header h2 {
    font-family: var(--font-mono);
    font-size: 1.5rem;
    flex: 1;
}

.course-progress-bar {
    height: 8px;
    background: var(--bg-card);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 0.5rem;
}

.progress-label {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.curriculum-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.curriculum-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.25rem;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.15s ease;
}

.curriculum-item:hover:not(.locked) {
    border-color: var(--border-light);
    background: var(--bg-hover);
}

.curriculum-item.locked {
    opacity: 0.5;
    cursor: not-allowed;
}

.curriculum-item.locked .curriculum-number {
    background: var(--bg-secondary);
    color: var(--text-muted);
}

.curriculum-item.locked .lock-icon {
    margin-left: auto;
    color: var(--text-muted);
    font-size: 1rem;
}

.curriculum-progress {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-left: auto;
}

.curriculum-icons {
    font-size: 0.8rem;
    opacity: 0.7;
}

.curriculum-item.completed {
    border-color: var(--correct);
    background: var(--correct-bg);
}

.curriculum-item.current {
    border-color: var(--accent);
    background: var(--accent-glow);
}

.curriculum-number {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    width: 2rem;
    height: 2rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    border-radius: 50%;
    color: var(--text-muted);
    flex-shrink: 0;
}

.curriculum-item.completed .curriculum-number {
    background: var(--correct);
    color: var(--bg-primary);
}

.curriculum-item.current .curriculum-number {
    background: var(--accent);
    color: var(--bg-primary);
}

.curriculum-info {
    flex: 1;
}

.curriculum-title {
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.curriculum-topic {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-muted);
}

.curriculum-status {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    padding: 0.25rem 0.5rem;
    border-radius: var(--radius-sm);
    color: var(--text-muted);
}

.curriculum-item.completed .curriculum-status {
    background: var(--correct-bg);
    color: var(--correct);
}

.curriculum-item.current .curriculum-status {
    background: var(--accent-glow);
    color: var(--accent);
}

/* ============================================
   Video Lesson Screen
   ============================================ */

.lesson-badge {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    padding: 0.375rem 0.75rem;
    background: var(--accent-glow);
    color: var(--accent);
    border-radius: var(--radius-sm);
    border: 1px solid rgba(0, 212, 170, 0.3);
}

.lesson-content {
    max-width: 800px;
    margin: 0 auto;
}

.lesson-content h2 {
    font-family: var(--font-mono);
    font-size: 1.75rem;
    margin-bottom: 0.75rem;
}

.lesson-description {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.6;
}

.video-container {
    position: relative;
    width: 100%;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin-bottom: 2rem;
    border: 1px solid var(--border);
}

.video-placeholder {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    cursor: pointer;
    transition: background 0.2s ease;
}

.video-placeholder:hover {
    background: var(--bg-hover);
}

.play-icon {
    font-size: 3rem;
    color: var(--accent);
}

.video-placeholder span:last-child {
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--text-muted);
}

#youtube-player {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: none;
}

#youtube-player iframe {
    width: 100%;
    height: 100%;
}

.lesson-progress {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    margin-bottom: 2rem;
    padding: 1rem;
    background: var(--bg-card);
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
}

.progress-step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-muted);
    transition: all 0.2s ease;
}

.progress-step .step-icon {
    font-size: 1.1rem;
}

.progress-step.completed {
    color: var(--correct);
    background: var(--correct-bg);
}

.progress-step.completed .step-icon::before {
    content: '✓';
}

.progress-step.completed .step-icon {
    font-size: 0;
}

.progress-step.completed .step-icon::before {
    font-size: 1.1rem;
}

.progress-connector {
    width: 2rem;
    height: 2px;
    background: var(--border);
}

.lesson-actions {
    text-align: center;
}

/* Topic Complete Message */
.topic-complete-msg {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    background: var(--correct-bg);
    border: 1px solid var(--correct);
    border-radius: var(--radius-md);
    color: var(--correct);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    margin-top: 1.5rem;
}

.topic-complete-msg.hidden {
    display: none;
}

.complete-icon {
    font-size: 1.25rem;
}

/* ============================================
   Quiz Screen
   ============================================ */

.quiz-header {
    margin-bottom: 2rem;
}

.quiz-header .btn-back {
    margin-bottom: 1rem;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

#question-counter {
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.topic-badge {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 0.25rem 0.625rem;
    background: var(--accent-glow);
    color: var(--accent);
    border-radius: var(--radius-sm);
    border: 1px solid rgba(0, 212, 170, 0.3);
}

.progress-bar {
    height: 4px;
    background: var(--bg-card);
    border-radius: 2px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent);
    border-radius: 2px;
    width: 0%;
    transition: width 0.3s ease;
    box-shadow: 0 0 10px var(--accent);
}

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

.question-text {
    font-size: 1.125rem;
    line-height: 1.7;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.question-text code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    padding: 0.125rem 0.375rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
    color: var(--accent);
}

.question-image {
    margin-bottom: 1.5rem;
    text-align: center;
}

.question-image img {
    max-width: 100%;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
}

.question-image:empty {
    display: none;
}

/* Choices */
.choices {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.choice {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    padding: 1rem 1.25rem;
    background: var(--bg-secondary);
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.15s ease;
    text-align: left;
    font-family: var(--font-sans);
    font-size: 1rem;
    color: var(--text-primary);
    width: 100%;
}

.choice:hover:not(.disabled) {
    border-color: var(--border-light);
    background: var(--bg-hover);
}

.choice.disabled {
    cursor: default;
}

.choice-letter {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    width: 1.75rem;
    height: 1.75rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-card);
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    flex-shrink: 0;
    transition: all 0.15s ease;
}

.choice:hover:not(.disabled) .choice-letter {
    color: var(--accent);
    background: var(--accent-glow);
}

.choice-text {
    flex: 1;
    padding-top: 0.125rem;
}

/* Choice States */
.choice.selected {
    border-color: var(--accent);
    background: var(--accent-glow);
}

.choice.selected .choice-letter {
    background: var(--accent);
    color: var(--bg-primary);
}

.choice.correct {
    border-color: var(--correct);
    background: var(--correct-bg);
}

.choice.correct .choice-letter {
    background: var(--correct);
    color: var(--bg-primary);
}

.choice.incorrect {
    border-color: var(--incorrect);
    background: var(--incorrect-bg);
}

.choice.incorrect .choice-letter {
    background: var(--incorrect);
    color: var(--bg-primary);
}

/* Quiz Footer */
.quiz-footer {
    display: flex;
    justify-content: flex-end;
}

/* ============================================
   Results Screen
   ============================================ */

.results-header {
    text-align: center;
    padding: 2rem 0 3rem;
}

.results-header h2 {
    font-family: var(--font-mono);
    font-size: 2rem;
    margin-bottom: 2rem;
}

.score-display {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.score-circle {
    font-family: var(--font-mono);
    font-size: 4rem;
    font-weight: 700;
    display: flex;
    align-items: baseline;
    gap: 0.25rem;
    color: var(--accent);
    text-shadow: 0 0 40px var(--accent-glow);
}

.score-total {
    font-size: 1.5rem;
    color: var(--text-muted);
    font-weight: 400;
}

.score-message {
    font-size: 1.125rem;
    color: var(--text-secondary);
}

/* Stats Display */
.stats-display {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border);
}

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
}

.stat-value {
    font-family: var(--font-mono);
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--accent);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.btn-danger {
    color: var(--incorrect);
    border-color: var(--incorrect);
    margin-left: 1rem;
}

.btn-danger:hover {
    background: var(--incorrect-bg);
    border-color: var(--incorrect);
    color: var(--incorrect);
}

/* Review Section */
.results-review {
    margin-bottom: 2rem;
}

.results-review h3 {
    font-family: var(--font-mono);
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 1.25rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border);
}

.review-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.review-item {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.review-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.25rem;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    cursor: pointer;
    transition: background 0.15s ease;
}

.review-header:hover {
    background: var(--bg-hover);
}

.review-status {
    width: 1.5rem;
    height: 1.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    flex-shrink: 0;
}

.review-status.correct {
    background: var(--correct-bg);
    color: var(--correct);
    border: 1px solid var(--correct);
}

.review-status.incorrect {
    background: var(--incorrect-bg);
    color: var(--incorrect);
    border: 1px solid var(--incorrect);
}

.review-question {
    flex: 1;
    font-size: 0.95rem;
    color: var(--text-primary);
    line-height: 1.5;
}

.review-toggle {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-muted);
    transition: transform 0.2s ease;
}

.review-item.expanded .review-toggle {
    transform: rotate(180deg);
}

.review-body {
    display: none;
    padding: 1.25rem;
}

.review-item.expanded .review-body {
    display: block;
}

.review-image {
    margin-bottom: 1rem;
    text-align: center;
}

.review-image img {
    max-width: 100%;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
}

.review-answers {
    margin-bottom: 1rem;
}

.review-answer {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    padding: 0.625rem 0.875rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.review-answer:last-child {
    margin-bottom: 0;
}

.review-answer.user-correct {
    background: var(--correct-bg);
    color: var(--correct);
}

.review-answer.user-incorrect {
    background: var(--incorrect-bg);
    color: var(--incorrect);
}

.review-answer.actual-correct {
    background: var(--correct-bg);
    color: var(--correct);
}

.review-label {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    flex-shrink: 0;
    padding-top: 0.125rem;
}

.review-explanation {
    background: var(--bg-secondary);
    border-left: 3px solid var(--accent);
    padding: 1rem 1.25rem;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.review-explanation-label {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--accent);
    margin-bottom: 0.5rem;
}

.review-explanation p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.review-explanation code {
    font-family: var(--font-mono);
    font-size: 0.85em;
    padding: 0.125rem 0.375rem;
    background: var(--bg-card);
    border-radius: var(--radius-sm);
    color: var(--accent);
}

/* Results Footer */
.results-footer {
    text-align: center;
    padding-top: 1rem;
}

/* ============================================
   Ko-fi Button
   ============================================ */

.kofi-container {
    display: flex;
    justify-content: center;
    margin-top: 2rem;
}

.support-prompt {
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border);
    text-align: center;
}

.support-prompt p {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 1rem;
}

.support-prompt .kofi-container {
    margin-top: 0;
}

/* Override Ko-fi button text color */
.kofi-button {
    color: #0a0e14 !important;
}

.kofi-button span.kofitext {
    color: #0a0e14 !important;
}

/* ============================================
   MathJax Overrides
   ============================================ */

.MathJax {
    font-size: 1.1em !important;
}

/* ============================================
   Responsive
   ============================================ */

@media (max-width: 640px) {
    .container {
        padding: 1.5rem 1rem;
    }
    
    .hero {
        padding: 2rem 0;
    }
    
    .logo {
        font-size: 1.25rem;
    }
    
    .channel-link {
        padding: 0.375rem 0.75rem 0.375rem 0.375rem;
        gap: 0.5rem;
    }
    
    .yt-logo {
        width: 26px;
        height: 26px;
        font-size: 0.75rem;
    }
    
    .channel-name {
        font-size: 0.8rem;
    }
    
    .hero h1 {
        font-size: 1.75rem;
    }
    
    .question-card {
        padding: 1.5rem 1.25rem;
    }
    
    .choice {
        padding: 0.875rem 1rem;
    }
    
    .score-circle {
        font-size: 3rem;
    }
}