:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --accent: #f59e0b;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f5f9;
    
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    
    --border: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 10px 10px -5px rgba(0,0,0,0.04);
    
    --radius-sm: 6px;
    --radius: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    
    --transition: all 0.2s ease;
    --transition-slow: all 0.3s ease;
}

[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --border: #334155;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
    --shadow: 0 4px 6px -1px rgba(0,0,0,0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.4);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.app-container {
    display: flex;
    flex-direction: column;
    height: 100%;
}

/* ==================== HEADER ==================== */
.main-header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    padding: 0.75rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo-icon {
    font-size: 1.5rem;
}

.logo-text {
    font-size: 1.25rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.badge {
    background: linear-gradient(135deg, var(--accent), #fbbf24);
    color: #1e293b;
    font-size: 0.65rem;
    font-weight: 700;
    padding: 0.2rem 0.5rem;
    border-radius: 999px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.main-nav {
    display: flex;
    gap: 0.5rem;
    background: var(--bg-tertiary);
    padding: 0.25rem;
    border-radius: var(--radius);
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    padding: 0.6rem 1rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    font-weight: 500;
    font-size: 0.9rem;
}

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

.nav-btn.active {
    background: var(--bg-secondary);
    color: var(--primary);
    box-shadow: var(--shadow-sm);
}

.nav-icon {
    font-size: 1.1rem;
}

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

.progress-indicator {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.progress-ring {
    position: relative;
    width: 40px;
    height: 40px;
}

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

.progress-ring-bg {
    fill: none;
    stroke: var(--bg-tertiary);
    stroke-width: 3;
}

.progress-ring-fill {
    fill: none;
    stroke: var(--primary);
    stroke-width: 3;
    stroke-linecap: round;
    transition: stroke-dasharray 0.5s ease;
}

.progress-ring span {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 0.6rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.icon-btn {
    width: 40px;
    height: 40px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    background: var(--bg-secondary);
    cursor: pointer;
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.icon-btn:hover {
    background: var(--bg-tertiary);
    border-color: var(--primary);
}

/* ==================== MODE CONTAINERS ==================== */
.mode-container {
    flex: 1;
    display: flex;
    overflow: hidden;
}

.hidden {
    display: none !important;
}

/* ==================== STUDY MODE ==================== */
#study-mode {
    display: flex;
}

.chapter-list {
    width: 280px;
    background: var(--bg-secondary);
    display: flex;
    flex-direction: column;
    border-right: 1px solid var(--border);
}

.sidebar-header {
    padding: 1rem;
    border-bottom: 1px solid var(--border);
}

.sidebar-header h3 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
}

.search-box {
    position: relative;
}

.search-box input {
    width: 100%;
    padding: 0.6rem 0.75rem 0.6rem 2.25rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--bg-tertiary);
    color: var(--text-primary);
    font-size: 0.875rem;
    transition: var(--transition);
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary);
    background: var(--bg-secondary);
}

.search-box input::placeholder {
    color: var(--text-muted);
}

.search-icon {
    position: absolute;
    left: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    font-size: 0.9rem;
    opacity: 0.5;
}

#chapter-nav {
    list-style: none;
    flex: 1;
    overflow-y: auto;
    padding: 0.5rem;
}

#chapter-nav li {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 0.25rem;
}

#chapter-nav li:hover {
    background: var(--bg-tertiary);
}

#chapter-nav li.active {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
}

#chapter-nav li.read {
    opacity: 0.7;
}

#chapter-nav li.read::after {
    content: '✓';
    margin-left: auto;
    color: var(--success);
    font-weight: bold;
}

#chapter-nav li.active.read::after {
    color: white;
}

.chapter-num {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    flex-shrink: 0;
}

#chapter-nav li.active .chapter-num {
    background: rgba(255,255,255,0.2);
}

.sidebar-footer {
    padding: 1rem;
    border-top: 1px solid var(--border);
    text-align: center;
}

.stats-mini {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.chapter-content {
    flex: 1;
    padding: 2rem;
    overflow-y: auto;
    background: var(--bg-primary);
}

.paper-sheet {
    max-width: 800px;
    margin: 0 auto;
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
}

.chapter-header {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border);
}

.chapter-badge {
    width: 48px;
    height: 48px;
    border-radius: var(--radius);
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    font-weight: 700;
    flex-shrink: 0;
}

.chapter-meta {
    flex: 1;
}

.chapter-meta h1 {
    font-size: 1.5rem;
    font-weight: 700;
    line-height: 1.3;
    margin-bottom: 0.25rem;
}

.reading-time {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.bookmark-btn {
    width: 40px;
    height: 40px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    background: var(--bg-secondary);
    cursor: pointer;
    font-size: 1.25rem;
    transition: var(--transition);
}

.bookmark-btn:hover {
    border-color: var(--accent);
    background: rgba(245, 158, 11, 0.1);
}

.bookmark-btn.active {
    background: var(--accent);
    border-color: var(--accent);
}

.typography {
    font-family: 'Merriweather', Georgia, serif;
    line-height: 1.8;
    color: var(--text-primary);
}

.typography h3 {
    font-family: 'Inter', sans-serif;
    font-size: 1.1rem;
    font-weight: 600;
    margin-top: 2rem;
    margin-bottom: 0.75rem;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.typography h3::before {
    content: '';
    width: 4px;
    height: 1.2em;
    background: var(--primary);
    border-radius: 2px;
}

.typography p {
    margin-bottom: 1rem;
    font-size: 1rem;
}

.typography ol, .typography ul {
    margin-bottom: 1rem;
    padding-left: 1.5rem;
}

.typography li {
    margin-bottom: 0.5rem;
}

.typography em {
    color: var(--primary);
    font-style: italic;
}

.typography strong {
    background: linear-gradient(120deg, rgba(99, 102, 241, 0.15) 0%, rgba(99, 102, 241, 0.15) 100%);
    padding: 0.1rem 0.3rem;
    border-radius: 3px;
}

/* ==================== HIGHLIGHT BOXES ==================== */
.highlight-box {
    background: var(--bg-tertiary);
    border-left: 4px solid var(--primary);
    padding: 1rem 1.25rem;
    border-radius: 0 var(--radius) var(--radius) 0;
    margin: 1.25rem 0;
}

.highlight-box.warning {
    border-left-color: var(--warning);
    background: rgba(245, 158, 11, 0.1);
}

[data-theme="dark"] .highlight-box.warning {
    background: rgba(245, 158, 11, 0.15);
}

.highlight-box h4 {
    font-family: 'Inter', sans-serif;
    margin-top: 0;
    color: var(--primary);
    font-size: 1rem;
    margin-bottom: 0.5rem;
}

.highlight-box.warning h4 {
    color: var(--warning);
}

.highlight-box ul, .highlight-box ol {
    margin-bottom: 0;
}

.highlight-box p:last-child {
    margin-bottom: 0;
}

/* ==================== INFO TABLES ==================== */
.info-table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
    font-size: 0.95rem;
    font-family: 'Inter', sans-serif;
}

.info-table th, .info-table td {
    padding: 0.75rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

.info-table th {
    background: var(--bg-tertiary);
    font-weight: 600;
    color: var(--primary);
}

.info-table tr:last-child td {
    border-bottom: none;
}

.info-table tr:hover td {
    background: rgba(99, 102, 241, 0.05);
}

/* ==================== TWO COLUMN LAYOUT ==================== */
.two-columns {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin: 1.25rem 0;
}

.two-columns .column {
    background: var(--bg-tertiary);
    padding: 1rem 1.25rem;
    border-radius: var(--radius);
}

.two-columns .column h4 {
    font-family: 'Inter', sans-serif;
    margin-top: 0;
    color: var(--primary);
    border-bottom: 2px solid var(--primary);
    padding-bottom: 0.5rem;
    margin-bottom: 0.75rem;
    font-size: 1rem;
}

.two-columns .column.highlight-box {
    border-left: 4px solid var(--primary);
    border-radius: 0 var(--radius) var(--radius) 0;
}

.two-columns .column ul {
    margin-bottom: 0;
}

.chapter-actions {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border);
}

.action-btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    padding: 0.6rem 1.2rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.875rem;
    transition: var(--transition);
}

.action-btn:hover {
    background: var(--success);
    color: white;
    border-color: var(--success);
}

.action-btn.marked {
    background: var(--success);
    color: white;
    border-color: var(--success);
}

.navigation-footer {
    margin-top: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-arrow {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.25rem;
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    font-weight: 500;
    transition: var(--transition);
}

.nav-arrow:hover:not(:disabled) {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.nav-arrow:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

.chapter-dots {
    display: flex;
    gap: 0.5rem;
}

.chapter-dots .dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--border);
    transition: var(--transition);
}

.chapter-dots .dot.active {
    background: var(--primary);
    transform: scale(1.2);
}

.chapter-dots .dot.read {
    background: var(--success);
}

/* ==================== FLASHCARD MODE ==================== */
#flashcard-mode {
    justify-content: center;
    align-items: center;
    padding: 2rem;
    background: var(--bg-primary);
}

.flashcard-wrapper {
    width: 100%;
    max-width: 600px;
}

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

.flashcard-header h2 {
    font-size: 1.5rem;
    font-weight: 700;
}

.flashcard-progress {
    font-size: 0.9rem;
    color: var(--text-secondary);
    background: var(--bg-secondary);
    padding: 0.5rem 1rem;
    border-radius: var(--radius);
}

.flashcard-container {
    perspective: 1000px;
    margin-bottom: 1.5rem;
}

.flashcard {
    width: 100%;
    height: 300px;
    cursor: pointer;
    position: relative;
}

.flashcard-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.6s;
    transform-style: preserve-3d;
}

.flashcard.flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-front, .flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    box-shadow: var(--shadow-lg);
}

.flashcard-front {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
}

.flashcard-back {
    background: var(--bg-secondary);
    color: var(--text-primary);
    transform: rotateY(180deg);
    border: 2px solid var(--primary);
}

.flip-hint {
    position: absolute;
    top: 1rem;
    font-size: 0.75rem;
    opacity: 0.7;
}

#fc-term {
    font-size: 1.5rem;
    font-weight: 700;
}

#fc-definition {
    font-size: 1.1rem;
    line-height: 1.6;
    font-family: 'Merriweather', serif;
}

.flashcard-controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.fc-btn {
    padding: 0.75rem 1.5rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    font-weight: 500;
    transition: var(--transition);
}

.fc-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

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

.fc-btn.secondary:hover {
    background: var(--bg-tertiary);
}

.flashcard-stats {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.stat-btn {
    padding: 0.6rem 1.25rem;
    border: 2px solid;
    border-radius: var(--radius);
    background: transparent;
    cursor: pointer;
    font-weight: 500;
    transition: var(--transition);
}

.stat-btn.green {
    border-color: var(--success);
    color: var(--success);
}

.stat-btn.green:hover {
    background: var(--success);
    color: white;
}

.stat-btn.red {
    border-color: var(--danger);
    color: var(--danger);
}

.stat-btn.red:hover {
    background: var(--danger);
    color: white;
}

/* ==================== QUIZ MODE ==================== */
#quiz-mode {
    justify-content: center;
    align-items: flex-start;
    padding: 2rem;
    overflow-y: auto;
    background: var(--bg-primary);
}

.quiz-wrapper {
    width: 100%;
    max-width: 700px;
    margin: 0 auto;
}

.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--bg-secondary);
    padding: 1.25rem 1.5rem;
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    border: 1px solid var(--border);
    border-bottom: none;
}

.quiz-title h2 {
    font-size: 1.25rem;
    margin-bottom: 0.25rem;
}

.quiz-subtitle {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.quiz-meta {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.timer {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-secondary);
    font-variant-numeric: tabular-nums;
}

.score-board {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.score-label {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.score-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary);
}

.quiz-progress-bar {
    height: 4px;
    background: var(--border);
}

.quiz-progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--primary-light));
    transition: width 0.3s ease;
    width: 0%;
}

.quiz-card {
    background: var(--bg-secondary);
    padding: 2rem;
    border: 1px solid var(--border);
    border-top: none;
    border-radius: 0 0 var(--radius-lg) var(--radius-lg);
}

.question-text {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

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

.option-btn {
    padding: 1rem 1.25rem;
    border: 2px solid var(--border);
    background: var(--bg-secondary);
    text-align: left;
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 1rem;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.option-btn:hover:not(:disabled) {
    border-color: var(--primary);
    background: rgba(99, 102, 241, 0.05);
}

.option-btn .option-letter {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.85rem;
    flex-shrink: 0;
}

.option-btn.correct {
    background: rgba(16, 185, 129, 0.1);
    border-color: var(--success);
    color: var(--text-primary);
}

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

.option-btn.wrong {
    background: rgba(239, 68, 68, 0.1);
    border-color: var(--danger);
}

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

.explanation {
    margin-top: 1.5rem;
    padding: 1.25rem;
    background: rgba(245, 158, 11, 0.1);
    border: 1px solid var(--warning);
    border-radius: var(--radius);
    animation: slideUp 0.3s ease;
}

.explanation strong {
    color: var(--warning);
}

.next-btn {
    margin-top: 1rem;
    padding: 0.75rem 1.5rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    font-weight: 500;
    float: right;
    transition: var(--transition);
}

.next-btn:hover {
    background: var(--primary-dark);
}

.quiz-result {
    background: var(--bg-secondary);
    padding: 3rem 2rem;
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.result-icon {
    font-size: 4rem;
    margin-bottom: 1rem;
}

.result-grade {
    font-size: 5rem;
    font-weight: 800;
    margin: 1rem 0;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.result-stats {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin: 2rem 0;
}

.stat-item {
    text-align: center;
}

.stat-item .value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary);
}

.stat-item .label {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.restart-btn {
    margin-top: 1.5rem;
    padding: 1rem 2.5rem;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: var(--transition);
}

.restart-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

/* ==================== TOAST NOTIFICATIONS ==================== */
.toast-container {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.toast {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    padding: 1rem 1.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    animation: slideIn 0.3s ease;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.toast.success {
    border-left: 4px solid var(--success);
}

.toast.error {
    border-left: 4px solid var(--danger);
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

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

/* ==================== RESPONSIVE ==================== */
@media (max-width: 900px) {
    .main-header {
        flex-wrap: wrap;
        gap: 0.75rem;
    }
    
    .nav-text {
        display: none;
    }
    
    .nav-btn {
        padding: 0.6rem 0.8rem;
    }
}

@media (max-width: 768px) {
    #study-mode {
        flex-direction: column;
    }
    
    .chapter-list {
        width: 100%;
        max-height: 200px;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }
    
    .chapter-content {
        padding: 1rem;
    }
    
    .paper-sheet {
        padding: 1.5rem;
    }
    
    .chapter-header {
        flex-wrap: wrap;
    }
    
    .chapter-dots {
        display: none;
    }
    
    .flashcard {
        height: 250px;
    }
    
    .quiz-header {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }
    
    .two-columns {
        grid-template-columns: 1fr;
    }
    
    .info-table {
        font-size: 0.85rem;
    }
    
    .info-table th, .info-table td {
        padding: 0.5rem 0.75rem;
    }
}