/* Dark Mode Color Palette */
:root {
    --primary-color: #8A2BE2; /* A vibrant purple for the main accent */
    --primary-light: #9370DB; /* A lighter shade of purple */
    --primary-dark: #4B0082; /* A deep indigo for dark accents */
    --secondary-color: #1E1E1E; /* A slightly lighter dark color for secondary elements */
    --accent-color: #00FF7F; /* A bright green for success states */
    --warning-color: #FFD700; /* Gold for warnings */
    --danger-color: #FF4500; /* Orange-Red for errors */
    --text-primary: #E0E0E0; /* A light gray for primary text */
    --text-secondary: #B0B0B0; /* A slightly darker gray for secondary text */
    --text-light: #888888; /* A darker gray for less important text */
    --background: #121212; /* A pure black for the main background */
    --background-alt: #1A1A1A; /* A slightly lighter black for alternate backgrounds */
    --border-color: #2A2A2A; /* A dark gray for borders */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.2);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.3), 0 2px 4px -2px rgb(0 0 0 / 0.3);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.4), 0 4px 6px -4px rgb(0 0 0 / 0.4);
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 16px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--background-alt);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Loading Screen */
.loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--background);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.loading-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top: 3px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 1rem;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.loading-screen p {
    color: var(--text-secondary);
    font-weight: 500;
}

/* Category Selection Screen */
.category-selection {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    background: var(--background);
}

.category-selection.hidden {
    display: none;
}

.category-container {
    max-width: 900px;
    width: 100%;
    text-align: center;
}

.category-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    letter-spacing: -0.025em;
}

.category-subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 3rem;
    font-weight: 400;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    justify-items: center;
}

.category-card {
    background: var(--background-alt);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
    width: 100%;
    max-width: 320px;
    box-shadow: var(--shadow-sm);
    position: relative;
    overflow: hidden;
}

.category-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--primary-color);
    transform: scaleX(0);
    transition: transform 0.2s ease;
}

.category-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.category-card:hover::before {
    transform: scaleX(1);
}

.category-card:active {
    transform: translateY(0);
}

.category-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    display: block;
    opacity: 0.9;
}

.category-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    letter-spacing: -0.015em;
}

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

.question-count {
    background: var(--secondary-color);
    color: var(--text-secondary);
    padding: 0.25rem 0.75rem;
    border-radius: 50px;
    font-size: 0.8rem;
    font-weight: 500;
    display: inline-block;
}

/* App Container */
.app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background: var(--background);
}

.app.hidden {
    display: none;
}

/* Header */
.header {
    background: var(--background-alt);
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.5rem;
    max-width: 1200px;
    margin: 0 auto;
}

.menu-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    transition: background-color 0.2s ease;
    display: flex;
    flex-direction: column;
    gap: 3px;
}

.menu-btn:hover {
    background: var(--secondary-color);
}

.menu-btn span {
    width: 20px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 1px;
    transition: all 0.2s ease;
}

.app-title-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
    flex: 1;
    margin: 0 1rem;
}

.app-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
    letter-spacing: -0.015em;
}

.category-badge {
    background: var(--primary-color);
    color: #FFFFFF;
    padding: 0.125rem 0.5rem;
    border-radius: var(--radius-sm);
    font-size: 0.7rem;
    font-weight: 500;
}

.category-switch-container {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--secondary-color);
    padding: 0.5rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.quiz-modes {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
    flex-wrap: wrap;
}

.mode-btn {
    background: var(--primary-color);
    color: #FFFFFF;
    border: none;
    padding: 0.4rem 0.8rem;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    flex: 1;
    min-width: fit-content;
}

.mode-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

.mode-btn:active {
    transform: translateY(0);
}

.category-dropdown {
    background: var(--secondary-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 0.4rem 0.8rem;
    font-size: 0.85rem;
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.2s ease;
    appearance: none;
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
    background-position: right 0.5rem center;
    background-repeat: no-repeat;
    background-size: 1rem;
    padding-right: 2rem;
}

.category-dropdown:hover {
    border-color: var(--primary-color);
    background-color: var(--background-alt);
}

.category-dropdown:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
    border-color: var(--primary-color);
}

.change-category-btn {
    background: var(--secondary-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 0.5rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.change-category-btn:hover {
    background: var(--background-alt);
    color: var(--text-primary);
    transform: scale(1.05);
}

.progress-indicator {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: var(--secondary-color);
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.progress-bar {
    height: 3px;
    background: var(--border-color);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary-color);
    transition: width 0.3s ease;
    width: 0%;
}

/* Sidebar */
.sidebar {
    position: fixed;
    top: 0;
    left: -320px;
    width: 320px;
    height: 100vh;
    background: var(--background-alt);
    border-right: 1px solid var(--border-color);
    transition: left 0.3s ease;
    z-index: 200;
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow-lg);
}

.sidebar.open {
    left: 0;
}

.sidebar h2 {
    margin-top: 0;
    color: #333;
    border-bottom: 1px solid #eee;
    padding-bottom: 10px;
}

.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-secondary);
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
}

.close-btn:hover {
    background: var(--background);
    color: var(--text-primary);
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-header h2 {
    margin: 0;
}

.sidebar-content {
    padding: 1.5rem;
    overflow-y: auto;
    flex-grow: 1;
}

.stats-section,
.navigation-section,
.actions-section {
    margin-bottom: 2rem;
}

.stats-section h3,
.navigation-section h3 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.stat-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
    font-size: 0.9rem;
}

.stat-item:last-child {
    border-bottom: none;
}

.stat-item span:first-child {
    color: var(--text-secondary);
}

.stat-item span:last-child {
    color: var(--text-primary);
    font-weight: 500;
}

/* Question Grid - Make it less overwhelming */
.question-grid {
    display: grid;
    grid-template-columns: repeat(10, 1fr);
    gap: 0.5rem;
    max-height: 200px;
    overflow-y: auto;
    padding: 0.5rem;
    background: var(--secondary-color);
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
}

.question-number-btn {
    width: 28px;
    height: 28px;
    border: 1px solid var(--border-color);
    background: var(--background);
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    color: var(--text-secondary);
}

.question-number-btn:hover {
    background: var(--primary-light);
    color: #FFFFFF;
    border-color: var(--primary-color);
}

.question-number-btn.current {
    background: var(--primary-color);
    color: #FFFFFF;
    border-color: var(--primary-color);
}

.question-number-btn.answered {
    background: var(--accent-color);
    color: #FFFFFF;
    border-color: var(--accent-color);
}

.question-number-btn.skipped {
    background: var(--warning-color);
    color: #FFFFFF;
    border-color: var(--warning-color);
}

/* Action Buttons */
.action-btn {
    width: 100%;
    padding: 0.75rem 1rem;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    margin-bottom: 0.5rem;
}

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

.action-btn.secondary:hover {
    background: var(--background);
    box-shadow: var(--shadow-sm);
}

.action-btn.danger {
    background: var(--danger-color);
    color: #FFFFFF;
}

.action-btn.danger:hover {
    background: #FF6347;
    box-shadow: var(--shadow-md);
}

/* Main Content */
.main-content {
    flex: 1;
    padding: 2rem;
    max-width: 800px;
    margin: 0 auto;
    width: 100%;
}

/* Question Card */
.question-card {
    background: var(--background-alt);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    margin-bottom: 2rem;
}

.question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    background: var(--secondary-color);
    border-bottom: 1px solid var(--border-color);
}

.question-number {
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
}

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

.bookmark-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.bookmark-btn:hover {
    background: var(--secondary-color);
    color: var(--warning-color);
}

.bookmark-btn.active {
    color: var(--warning-color);
    background: var(--secondary-color);
}

.question-content {
    padding: 2rem;
}

.question-text {
    font-size: 1.1rem;
    line-height: 1.7;
    color: var(--text-primary);
    margin: 0;
    font-weight: 500;
}

/* Answer Options */
.answer-options {
    padding: 0 2rem 2rem;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.answer-option {
    background: var(--secondary-color);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1rem 1.25rem;
    text-align: left;
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 0.95rem;
    line-height: 1.5;
    color: var(--text-primary);
    position: relative;
    overflow: hidden;
}

.answer-option::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--primary-color);
    transform: scaleY(0);
    transition: transform 0.2s ease;
}

.answer-option:hover {
    border-color: var(--primary-light);
    background: var(--background-alt);
}

.answer-option:hover::before {
    transform: scaleY(1);
}

.answer-option.selected {
    border-color: var(--primary-color);
    background: var(--primary-color);
    color: #FFFFFF;
}

.answer-option.selected::before {
    transform: scaleY(1);
    background: #FFFFFF;
}

.answer-option.correct {
    border-color: var(--accent-color);
    background: var(--accent-color);
    color: #FFFFFF;
}

.answer-option.incorrect {
    border-color: var(--danger-color);
    background: var(--danger-color);
    color: #FFFFFF;
}

/* Selected Answer Feedback */
.selected-answer {
    padding: 1.5rem 2rem;
    background: var(--secondary-color);
    border-top: 1px solid var(--border-color);
}

.answer-feedback,
.correct-answer {
    margin-bottom: 0.75rem;
}

.answer-feedback:last-child,
.correct-answer:last-child {
    margin-bottom: 0;
}

.feedback-label {
    font-weight: 600;
    color: var(--text-secondary);
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    display: block;
    margin-bottom: 0.25rem;
}

.user-answer,
.correct-answer-text {
    color: var(--text-primary);
    font-weight: 500;
}

/* Navigation Controls */
.nav-controls {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1rem;
    padding: 1.5rem 2rem;
    background: var(--background-alt);
    border-top: 1px solid var(--border-color);
    position: sticky;
    bottom: 0;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    min-width: 100px;
    justify-content: center;
}

.nav-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

.nav-btn.primary {
    background: var(--primary-color);
    color: #FFFFFF;
}

.nav-btn.primary:hover:not(:disabled) {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

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

.nav-btn.secondary:hover:not(:disabled) {
    background: var(--background);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.nav-btn svg {
    width: 16px;
    height: 16px;
}

/* Floating Action Button */
.fab {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 56px;
    height: 56px;
    background: var(--primary-color);
    color: #FFFFFF;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 50;
}

.fab:hover {
    background: var(--primary-dark);
    transform: scale(1.1);
    box-shadow: var(--shadow-lg);
}

.fab:active {
    transform: scale(0.95);
}

/* Overlay */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(2px);
    z-index: 150;
    opacity: 0;
    visibility: hidden;
    transition: all 0.2s ease;
}

.overlay.active {
    opacity: 1;
    visibility: visible;
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    top: 2rem;
    right: 2rem;
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.toast {
    background: var(--background-alt);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1rem;
    box-shadow: var(--shadow-lg);
    transform: translateX(100%);
    opacity: 0;
    transition: all 0.3s ease;
    min-width: 250px;
    max-width: 400px;
    font-size: 0.9rem;
    font-weight: 500;
}

.toast.show {
    transform: translateX(0);
    opacity: 1;
}

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

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

.toast.info {
    border-left: 4px solid var(--primary-color);
    color: var(--primary-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .category-title {
        font-size: 2rem;
    }
    
    .category-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
        max-width: 100%;
    }
    
    .category-card {
        max-width: none;
        padding: 1.5rem;
        margin: 0 auto;
        width: 100%;
    }
    
    .category-icon {
        font-size: 2.5rem;
    }
    
    .header-content {
        padding: 0.75rem 1rem;
        gap: 0.5rem;
        flex-wrap: nowrap;
    }
    
    .app-title-container {
        margin: 0 0.5rem;
        min-width: 0;
        flex: 1;
    }
    
    .app-title {
        font-size: 0.95rem;
        text-align: center;
    }
    
    .category-badge {
        font-size: 0.65rem;
        padding: 0.1rem 0.4rem;
    }
    
    .category-switch-container {
        padding: 0.4rem;
    }
    
    .category-dropdown {
        font-size: 0.8rem;
        padding: 0.3rem 1.5rem 0.3rem 0.6rem;
        max-width: 140px;
    }
    
    .progress-indicator {
        font-size: 0.8rem;
        padding: 0.4rem 0.6rem;
        white-space: nowrap;
    }
    
    .main-content {
        padding: 1rem;
    }
    
    .question-card {
        margin-bottom: 1rem;
        border-radius: var(--radius-md);
    }
    
    .question-header,
    .question-content {
        padding: 1rem;
    }
    
    .answer-options {
        padding: 0 1rem 1rem;
        gap: 0.75rem;
    }
    
    .answer-option {
        padding: 1rem 1.25rem;
        font-size: 0.95rem;
        min-height: 52px;
        border-radius: var(--radius-md);
        transition: all 0.2s ease;
    }
    
    .answer-option:active {
        transform: scale(0.98);
    }
    
    .nav-controls {
        padding: 1rem;
        gap: 0.75rem;
        position: sticky;
        bottom: 0;
        background: var(--background-alt);
        border-top: 1px solid var(--border-color);
        box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.1);
    }
    
    .nav-btn {
        padding: 0.75rem 1rem;
        font-size: 0.9rem;
        min-width: 90px;
        min-height: 44px;
        border-radius: var(--radius-md);
    }
    
    .fab {
        bottom: 1.5rem;
        right: 1rem;
        width: 52px;
        height: 52px;
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    }
    
    .toast-container {
        top: 1rem;
        right: 1rem;
        left: 1rem;
    }
    
    .toast {
        min-width: auto;
        font-size: 0.9rem;
    }
    
    .sidebar {
        width: 300px;
        left: -300px;
    }
    
    .question-grid {
        grid-template-columns: repeat(8, 1fr);
        max-height: 150px;
        gap: 0.4rem;
    }
    
    .question-number-btn {
        width: 30px;
        height: 30px;
        font-size: 0.75rem;
    }
    
    .menu-btn {
        padding: 0.6rem;
        min-width: 44px;
        min-height: 44px;
    }
    
    .bookmark-btn {
        padding: 0.6rem;
        min-width: 44px;
        min-height: 44px;
    }
}

@media (max-width: 480px) {
    .category-selection {
        padding: 1rem;
    }
    
    .category-title {
        font-size: 1.75rem;
        margin-bottom: 0.5rem;
    }
    
    .category-subtitle {
        font-size: 1rem;
        margin-bottom: 2rem;
    }
    
    .category-card {
        padding: 1.25rem;
    }
    
    .category-card h3 {
        font-size: 1.1rem;
    }
    
    .category-card p {
        font-size: 0.85rem;
    }
    
    .mode-btn {
        padding: 0.5rem 0.7rem;
        font-size: 0.7rem;
    }
    
    .header-content {
        padding: 0.5rem 0.75rem;
    }
    
    .app-title {
        font-size: 0.9rem;
    }
    
    .category-dropdown {
        max-width: 120px;
        font-size: 0.75rem;
    }
    
    .progress-indicator {
        font-size: 0.75rem;
        padding: 0.3rem 0.5rem;
    }
    
    .main-content {
        padding: 0.75rem;
    }
    
    .question-header,
    .question-content {
        padding: 0.75rem;
    }
    
    .question-text {
        font-size: 1rem;
        line-height: 1.6;
    }
    
    .answer-options {
        padding: 0 0.75rem 0.75rem;
        gap: 0.6rem;
    }
    
    .answer-option {
        padding: 0.875rem 1rem;
        font-size: 0.9rem;
        min-height: 48px;
        line-height: 1.4;
    }
    
    .selected-answer {
        padding: 1rem 0.75rem;
    }
    
    .nav-controls {
        padding: 0.75rem;
        gap: 0.5rem;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .nav-btn {
        padding: 0.75rem 1rem;
        font-size: 0.85rem;
        min-width: 85px;
        flex: 1;
        max-width: 120px;
    }
    
    .nav-btn svg {
        width: 14px;
        height: 14px;
    }
    
    .question-grid {
        grid-template-columns: repeat(6, 1fr);
        gap: 0.3rem;
    }
    
    .question-number-btn {
        width: 28px;
        height: 28px;
        font-size: 0.7rem;
    }
    
    .sidebar {
        width: 280px;
        left: -280px;
    }
    
    .sidebar-content {
        padding: 1rem;
    }
    
    .action-btn {
        padding: 0.75rem;
        font-size: 0.85rem;
    }
    
    .toast {
        padding: 0.75rem;
        font-size: 0.85rem;
    }
}

/* Extra small screens */
@media (max-width: 360px) {
    .category-title {
        font-size: 1.5rem;
    }
    
    .header-content {
        padding: 0.5rem;
    }
    
    .app-title-container {
        margin: 0 0.25rem;
    }
    
    .app-title {
        font-size: 0.85rem;
    }
    
    .category-dropdown {
        max-width: 100px;
        font-size: 0.7rem;
    }
    
    .progress-indicator {
        font-size: 0.7rem;
        padding: 0.25rem 0.4rem;
    }
    
    .main-content {
        padding: 0.5rem;
    }
    
    .question-header,
    .question-content {
        padding: 0.5rem;
    }
    
    .question-text {
        font-size: 0.95rem;
    }
    
    .answer-options {
        padding: 0 0.5rem 0.5rem;
    }
    
    .answer-option {
        padding: 0.75rem 0.875rem;
        font-size: 0.85rem;
    }
    
    .nav-controls {
        padding: 0.5rem;
        flex-direction: column;
    }
    
    .nav-btn {
        width: 100%;
        max-width: none;
        margin-bottom: 0.25rem;
    }
    
    .nav-btn:last-child {
        margin-bottom: 0;
    }
    
    .sidebar {
        width: 260px;
        left: -260px;
    }
}

/* Focus states for accessibility */
.category-card:focus,
.answer-option:focus,
.nav-btn:focus,
.menu-btn:focus,
.change-category-btn:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Mobile touch improvements */
@media (hover: none) and (pointer: coarse) {
    /* Better touch targets for mobile */
    .answer-option {
        min-height: 56px;
        padding: 1rem 1.25rem;
        margin-bottom: 0.5rem;
    }
    
    .nav-btn {
        min-height: 48px;
        padding: 0.875rem 1.25rem;
    }
    
    .category-card .mode-btn {
        min-height: 40px;
        padding: 0.625rem 1rem;
        margin: 0.25rem;
    }
    
    .menu-btn, .bookmark-btn, .close-btn {
        min-width: 48px;
        min-height: 48px;
    }
    
    /* Remove hover effects on touch devices */
    .answer-option:hover,
    .nav-btn:hover,
    .category-card:hover {
        transform: none;
        box-shadow: var(--shadow-sm);
    }
    
    /* Better active states for touch */
    .answer-option:active {
        transform: scale(0.98);
        background: var(--primary-color);
        color: #FFFFFF;
        border-color: var(--primary-color);
    }
    
    .nav-btn:active {
        transform: scale(0.96);
    }
    
    .category-card:active {
        transform: scale(0.98);
    }
}

/* Improve tap targets on all mobile devices */
@media (max-width: 768px) {
    /* Ensure all interactive elements have proper touch targets */
    button, .answer-option, .nav-btn, .category-card {
        -webkit-tap-highlight-color: rgba(138, 43, 226, 0.1);
    }
    
    /* Prevent text selection on interactive elements */
    .answer-option, .nav-btn, .category-card, .mode-btn {
        -webkit-user-select: none;
        -moz-user-select: none;
        -ms-user-select: none;
        user-select: none;
    }
    
    /* Better scrolling for mobile */
    .sidebar-content, .topics-page-list {
        -webkit-overflow-scrolling: touch;
        overflow-scrolling: touch;
    }
    
    /* Improve form elements on mobile */
    .category-dropdown {
        -webkit-appearance: none;
        background-size: 16px;
        background-position: right 0.75rem center;
    }
}

/* Prevent zoom on form fields on iOS */
@media screen and (-webkit-min-device-pixel-ratio: 0) {
    select, input[type="text"], input[type="email"], input[type="password"] {
        font-size: 16px;
    }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* High Contrast Mode */
@media (prefers-contrast: high) {
    :root {
        --border-color: #FFFFFF;
        --shadow-sm: none;
        --shadow-md: none;
        --shadow-lg: none;
    }
    
    .answer-option {
        border-width: 3px;
    }
}

/* Focus Styles */
button:focus-visible,
.answer-option:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Loading Animation for Question Transitions */
.question-card.loading {
    opacity: 0.6;
    pointer-events: none;
}

.question-card.loading .question-text {
    background: linear-gradient(90deg, transparent, var(--secondary-color), transparent);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
}

@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
} 

/* Topics to Review */
.topics-to-review {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.topics-to-review h3 {
    margin-top: 0;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

#uncheck-all-topics {
    width: 100%;
    margin-bottom: 1.5rem;
    background: var(--background);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}
#uncheck-all-topics:hover {
    background: var(--border-color);
    color: var(--text-primary);
}

.topic-category {
    margin-bottom: 1.5rem;
}

.topic-category:last-child {
    margin-bottom: 0;
}

.topic-category h4 {
    margin-top: 0;
    margin-bottom: 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.topic-item {
    display: flex;
    align-items: center;
    margin-bottom: 0.75rem;
}

.topic-item input[type="checkbox"] {
    -webkit-appearance: none;
    appearance: none;
    background-color: transparent;
    margin: 0;
    font: inherit;
    color: var(--text-secondary);
    width: 1.15em;
    height: 1.15em;
    border: 0.15em solid var(--text-secondary);
    border-radius: var(--radius-sm);
    transform: translateY(-0.075em);
    display: grid;
    place-content: center;
    cursor: pointer;
    margin-right: 0.75rem;
}

.topic-item input[type="checkbox"]::before {
    content: "";
    width: 0.65em;
    height: 0.65em;
    transform: scale(0);
    transition: 120ms transform ease-in-out;
    box-shadow: inset 1em 1em var(--primary-color);
    transform-origin: bottom left;
    clip-path: polygon(14% 44%, 0 65%, 50% 100%, 100% 16%, 80% 0%, 43% 62%);
}

.topic-item input[type="checkbox"]:checked::before {
    transform: scale(1);
}

.topic-item label {
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.2s ease;
    flex: 1;
}

.topic-item label.checked {
    text-decoration: line-through;
    color: var(--text-secondary);
    opacity: 0.7;
} 

.hidden { display:none !important; }

/* Full-page Study Checklist */
.topics-page {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--background-alt);
    z-index: 250;
    display: flex;
    flex-direction: column;
}

.topics-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    background: var(--secondary-color);
    position: sticky;
    top: 0;
    z-index: 1;
}

.topics-header h2 {
    margin: 0;
}

.topics-page-list {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
}

/* Re-use the topic-category / topic-item styles already defined earlier */ 

/* Mobile enhancements */
@media (max-width: 600px) {
    .topics-header {
        padding: 0.75rem 1rem;
    }
    .topics-page-list {
        padding: 1rem;
    }
    #uncheck-all-topics-page,
    .topics-header .action-btn {
        font-size: 0.9rem;
        padding: 0.4rem 0.8rem;
    }
    .topic-item {
        margin-bottom: 0.6rem;
    }
    .topic-item input[type="checkbox"] {
        width: 1.3em;
        height: 1.3em;
    }
    .topic-item label {
        font-size: 0.9rem;
    }
}