:root {
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --danger-color: #dc3545;
    --warning-color: #ffc107;
    --info-color: #17a2b8;
    
    --bg-color: #ffffff;
    --text-color: #333333;
    --card-bg: #f8f9fa;
    --border-color: #dee2e6;
    --shadow: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-lg: 0 4px 6px rgba(0,0,0,0.1);
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --card-bg: #2d2d2d;
    --border-color: #404040;
    --shadow: 0 2px 4px rgba(0,0,0,0.3);
    --shadow-lg: 0 4px 6px rgba(0,0,0,0.3);
}

/* Markdown Content Styling */
.markdown-content {
    line-height: 1.8;
    color: var(--text-color);
}

.markdown-content h1 {
    font-size: 2rem;
    margin-top: 2rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.5rem;
}

.markdown-content h2 {
    font-size: 1.75rem;
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--primary-color);
}

.markdown-content h3 {
    font-size: 1.5rem;
    margin-top: 1.25rem;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.markdown-content h4 {
    font-size: 1.25rem;
    margin-top: 1rem;
    margin-bottom: 0.5rem;
}

.markdown-content p {
    margin-bottom: 1rem;
}

.markdown-content ul,
.markdown-content ol {
    margin-left: 2rem;
    margin-bottom: 1rem;
}

.markdown-content li {
    margin-bottom: 0.5rem;
}

.markdown-content code {
    background-color: var(--card-bg);
    padding: 0.2rem 0.4rem;
    border-radius: 3px;
    font-family: 'Courier New', monospace;
    font-size: 0.9em;
    color: var(--primary-color);
    border: 1px solid var(--border-color);
}

.markdown-content pre {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 5px;
    padding: 1rem;
    overflow-x: auto;
    margin: 1rem 0;
}

.markdown-content pre code {
    background-color: transparent;
    padding: 0;
    border: none;
    color: var(--text-color);
    font-size: 0.9rem;
    display: block;
    white-space: pre;
    font-family: 'Courier New', 'Consolas', 'Monaco', monospace;
}

/* Override highlight.js styles for dark theme */
[data-theme="dark"] .markdown-content pre code {
    color: #e0e0e0;
}

.markdown-content blockquote {
    border-left: 4px solid var(--primary-color);
    padding-left: 1rem;
    margin: 1rem 0;
    color: var(--secondary-color);
    font-style: italic;
}

.markdown-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
}

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

.markdown-content table th {
    background-color: var(--card-bg);
    font-weight: bold;
    color: var(--primary-color);
}

.markdown-content table tr:nth-child(even) {
    background-color: var(--card-bg);
}

.markdown-content a {
    color: var(--primary-color);
    text-decoration: none;
}

.markdown-content a:hover {
    text-decoration: underline;
}

.markdown-content strong {
    font-weight: bold;
    color: var(--text-color);
}

.markdown-content em {
    font-style: italic;
}

.markdown-content hr {
    border: none;
    border-top: 2px solid var(--border-color);
    margin: 2rem 0;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

.navbar {
    background-color: var(--card-bg);
    padding: 1rem 0;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand h1 {
    font-size: 1.5rem;
    color: var(--primary-color);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: color 0.3s;
}

.nav-menu a:hover,
.nav-menu a.active {
    color: var(--primary-color);
}

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

.menu-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    z-index: 1001;
}

.hamburger {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--text-color);
    position: relative;
    transition: all 0.3s;
}

.hamburger::before,
.hamburger::after {
    content: '';
    position: absolute;
    width: 24px;
    height: 2px;
    background-color: var(--text-color);
    transition: all 0.3s;
}

.hamburger::before {
    top: -7px;
}

.hamburger::after {
    top: 7px;
}

/* Hamburger animation when menu is open */
.menu-toggle.active .hamburger {
    background-color: transparent;
}

.menu-toggle.active .hamburger::before {
    transform: rotate(45deg);
    top: 0;
}

.menu-toggle.active .hamburger::after {
    transform: rotate(-45deg);
    top: 0;
}

/* Mobile Menu Overlay */
.mobile-menu {
    display: none;
    flex-direction: column;
    background-color: var(--card-bg);
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    padding: 1rem 0;
    box-shadow: var(--shadow-lg);
    border-top: 1px solid var(--border-color);
    z-index: 999;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, padding 0.3s ease;
}

.mobile-menu.show {
    max-height: 300px;
    padding: 1rem 0;
}

.mobile-menu a {
    padding: 0.75rem 2rem;
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: all 0.3s;
    border-left: 3px solid transparent;
}

.mobile-menu a:hover,
.mobile-menu a.active {
    color: var(--primary-color);
    background-color: var(--bg-color);
    border-left-color: var(--primary-color);
}

.theme-toggle {
    background: none;
    border: 2px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1.2rem;
    transition: all 0.3s;
}

.theme-toggle:hover {
    background-color: var(--primary-color);
    color: white;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

.hero-section {
    text-align: center;
    padding: 4rem 0;
}

.hero-section h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.hero-section p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    color: var(--secondary-color);
}

/* ==================== Modern Search Box ==================== */
.search-box {
    display: flex;
    max-width: 600px;
    margin: 0 auto;
    gap: 0.5rem;
    align-items: center;
}

.search-box input {
    flex: 1;
    padding: 1rem 1.5rem;
    border: none;
    border-radius: 50px;
    font-size: 1rem;
    background: var(--card-bg);
    color: var(--text-color);
    outline: none;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.06), 0 2px 8px rgba(0, 0, 0, 0.04);
    transition: all 0.3s ease;
}

.search-box input:focus {
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.06), 0 0 0 3px rgba(0, 123, 255, 0.15);
}

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

.search-box button {
    padding: 1rem 2rem;
    background: linear-gradient(135deg, var(--primary-color), #0056b3);
    color: white;
    border: none;
    border-radius: 50px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 600;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    box-shadow: 0 4px 15px rgba(0, 123, 255, 0.3);
}

.search-box button:hover {
    background: linear-gradient(135deg, #0056b3, #004494);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 123, 255, 0.4);
}

.search-box button:active {
    transform: translateY(0);
}

.stats-section {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    margin: 3rem 0;
}

.stat-card {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 10px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.stat-card.clickable {
    cursor: pointer;
    border: 2px solid transparent;
}

.stat-card.clickable:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
    background: linear-gradient(135deg, var(--card-bg) 0%, rgba(0, 123, 255, 0.05) 100%);
}

.stat-card.clickable:active {
    transform: translateY(-4px);
}

.stat-card .stat-icon {
    font-size: 2.5rem;
    margin-bottom: 0.75rem;
    display: block;
}

.stat-card h3 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.stat-card p {
    color: var(--text-color);
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.stat-card .stat-link {
    display: inline-block;
    margin-top: 0.75rem;
    font-size: 0.85rem;
    color: var(--primary-color);
    font-weight: 600;
    opacity: 0;
    transform: translateY(10px);
    transition: all 0.3s ease;
}

.stat-card.clickable:hover .stat-link {
    opacity: 1;
    transform: translateY(0);
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 1rem;
    margin: 2rem 0;
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.topic-card,
.category-card {
    background-color: var(--card-bg);
    padding: 1.5rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
    transition: all 0.3s;
    cursor: pointer;
}

.topic-card:hover,
.category-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

/* Compact Category Card Styles */
.category-card-compact {
    background-color: var(--card-bg);
    padding: 1rem 1.25rem;
    border-radius: 8px;
    box-shadow: var(--shadow);
    transition: all 0.3s;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    min-height: 90px;
}

.category-card-compact:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    border-left: 3px solid var(--primary-color);
}

.category-card-compact .category-name {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-color);
    margin: 0;
    line-height: 1.3;
}

.category-card-compact .category-topic-count {
    font-size: 0.8rem;
    color: var(--secondary-color);
}

/* Level Chip Styles */
.level-chip {
    display: inline-block;
    padding: 0.2rem 0.6rem;
    border-radius: 12px;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.3px;
    width: fit-content;
    margin-top: auto;
}

.level-chip.level-beginner {
    background: linear-gradient(135deg, #4CAF50, #45a049);
    color: white;
    box-shadow: 0 2px 4px rgba(76, 175, 80, 0.3);
}

.level-chip.level-intermediate {
    background: linear-gradient(135deg, #FF9800, #F57C00);
    color: white;
    box-shadow: 0 2px 4px rgba(255, 152, 0, 0.3);
}

.level-chip.level-advanced {
    background: linear-gradient(135deg, #f44336, #d32f2f);
    color: white;
    box-shadow: 0 2px 4px rgba(244, 67, 54, 0.3);
}

.level-chip.level-expert {
    background: linear-gradient(135deg, #9C27B0, #7B1FA2);
    color: white;
    box-shadow: 0 2px 4px rgba(156, 39, 176, 0.3);
}

.topic-card h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

/* Topic Card with Order Number */
.topic-card-ordered {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
}

.topic-order-badge {
    min-width: 36px;
    height: 36px;
    background: linear-gradient(135deg, var(--primary-color), #0056b3);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.9rem;
    flex-shrink: 0;
    box-shadow: 0 2px 4px rgba(0, 123, 255, 0.3);
}

.topic-card-content {
    flex: 1;
}

/* Category Group Styles */
.category-group {
    margin-bottom: 2.5rem;
}

.category-group-title {
    font-size: 1.3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.category-group-title::before {
    content: '📚';
}

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

/* Topic Details Page Styles */
.topic-breadcrumb {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.topic-breadcrumb a {
    color: var(--primary-color);
    text-decoration: none;
}

.topic-breadcrumb a:hover {
    text-decoration: underline;
}

.topic-breadcrumb span {
    color: var(--secondary-color);
}

.topic-breadcrumb .current {
    color: var(--text-color);
    font-weight: 500;
}

.topic-position-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    background: linear-gradient(135deg, #e3f2fd, #bbdefb);
    color: #1565c0;
    border: 1px solid #90caf9;
    padding: 0.3rem 0.75rem;
    border-radius: 15px;
    font-size: 0.75rem;
    font-weight: 600;
}

.topic-position-badge::before {
    content: '📖';
    font-size: 0.7rem;
}

[data-theme="dark"] .topic-position-badge {
    background: linear-gradient(135deg, rgba(33, 150, 243, 0.2), rgba(33, 150, 243, 0.1));
    color: #64b5f6;
    border-color: rgba(33, 150, 243, 0.3);
}

.category-tag {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    background: linear-gradient(135deg, #f3e5f5, #e1bee7);
    color: #7b1fa2;
    border: 1px solid #ce93d8;
    padding: 0.3rem 0.75rem;
    border-radius: 15px;
    font-size: 0.75rem;
    font-weight: 600;
}

.category-tag::before {
    content: '📁';
    font-size: 0.7rem;
}

[data-theme="dark"] .category-tag {
    background: linear-gradient(135deg, rgba(156, 39, 176, 0.2), rgba(156, 39, 176, 0.1));
    color: #ba68c8;
    border-color: rgba(156, 39, 176, 0.3);
}

/* Topic Navigation (Prev/Next) */
.topic-navigation {
    margin-top: 3rem;
    padding: 2rem;
    background-color: var(--card-bg);
    border-radius: 10px;
    border: 1px solid var(--border-color);
}

.topic-nav-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: 1.5rem;
    text-align: center;
}

.topic-nav-links {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.topic-nav-link {
    display: flex;
    flex-direction: column;
    padding: 1.25rem;
    background-color: var(--bg-color);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-color);
    transition: all 0.3s ease;
}

.topic-nav-link:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.topic-nav-prev {
    text-align: left;
}

.topic-nav-next {
    text-align: right;
}

.topic-nav-placeholder {
    background: transparent;
    border: 2px dashed var(--border-color);
}

.topic-nav-complete {
    text-align: center;
    background: linear-gradient(135deg, rgba(40, 167, 69, 0.1), rgba(40, 167, 69, 0.05));
    border-color: var(--success-color);
}

.nav-direction {
    font-size: 0.85rem;
    color: var(--primary-color);
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.nav-topic-title {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-color);
    margin-bottom: 0.25rem;
    line-height: 1.3;
}

.nav-topic-order {
    font-size: 0.8rem;
    color: var(--secondary-color);
}

.nav-back-link {
    color: var(--success-color);
    text-decoration: none;
    font-weight: 500;
    margin-top: 0.5rem;
    display: inline-block;
}

.nav-back-link:hover {
    text-decoration: underline;
}

/* Progress Bar */
.topic-progress {
    margin-top: 1.5rem;
    text-align: center;
}

.progress-text {
    font-size: 0.85rem;
    color: var(--secondary-color);
    margin-bottom: 0.5rem;
}

.progress-bar-container {
    width: 100%;
    height: 8px;
    background-color: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
}

.progress-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--success-color));
    border-radius: 4px;
    transition: width 0.5s ease;
}

/* Difficulty Level Chip Styles */
.badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.3rem 0.75rem;
    border-radius: 15px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.3px;
}

.badge.basic {
    background: linear-gradient(135deg, #e8f5e9, #c8e6c9);
    color: #2e7d32;
    border: 1px solid #a5d6a7;
}

.badge.basic::before {
    content: '●';
    font-size: 0.5rem;
    color: #4caf50;
}

.badge.intermediate {
    background: linear-gradient(135deg, #fff3e0, #ffe0b2);
    color: #e65100;
    border: 1px solid #ffcc80;
}

.badge.intermediate::before {
    content: '●●';
    font-size: 0.5rem;
    letter-spacing: -2px;
    color: #ff9800;
}

.badge.advanced {
    background: linear-gradient(135deg, #ffebee, #ffcdd2);
    color: #c62828;
    border: 1px solid #ef9a9a;
}

.badge.advanced::before {
    content: '●●●';
    font-size: 0.5rem;
    letter-spacing: -2px;
    color: #f44336;
}

/* Dark theme adjustments for badges */
[data-theme="dark"] .badge.basic {
    background: linear-gradient(135deg, rgba(76, 175, 80, 0.2), rgba(76, 175, 80, 0.1));
    color: #81c784;
    border-color: rgba(76, 175, 80, 0.3);
}

[data-theme="dark"] .badge.intermediate {
    background: linear-gradient(135deg, rgba(255, 152, 0, 0.2), rgba(255, 152, 0, 0.1));
    color: #ffb74d;
    border-color: rgba(255, 152, 0, 0.3);
}

[data-theme="dark"] .badge.advanced {
    background: linear-gradient(135deg, rgba(244, 67, 54, 0.2), rgba(244, 67, 54, 0.1));
    color: #e57373;
    border-color: rgba(244, 67, 54, 0.3);
}

.topic-card .badge {
    margin-top: 0.5rem;
}

/* ==================== Page Header ==================== */
.page-header {
    margin-bottom: 2rem;
}

.page-header h1 {
    margin-bottom: 1.5rem;
    font-size: 2rem;
    color: var(--text-color);
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.page-header h1::before {
    content: '';
    width: 4px;
    height: 1.5em;
    background: linear-gradient(180deg, var(--primary-color), var(--info-color));
    border-radius: 2px;
}

/* ==================== Modern Filter Controls ==================== */
.filter-controls {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
    align-items: center;
    padding: 1.25rem 1.5rem;
    background: linear-gradient(135deg, var(--card-bg) 0%, rgba(0, 123, 255, 0.02) 100%);
    border-radius: 16px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.06);
    border: 1px solid var(--border-color);
}

/* Modern Select Dropdown */
.filter-controls select,
select.modern-select {
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;
    padding: 0.75rem 2.75rem 0.75rem 1rem;
    border: none;
    border-radius: 12px;
    background-color: var(--bg-color);
    background-image: 
        linear-gradient(135deg, transparent 50%, var(--primary-color) 50%),
        linear-gradient(225deg, transparent 50%, var(--primary-color) 50%);
    background-position: 
        calc(100% - 18px) calc(50% + 2px),
        calc(100% - 12px) calc(50% + 2px);
    background-size: 6px 6px, 6px 6px;
    background-repeat: no-repeat;
    color: var(--text-color);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.25s ease;
    min-width: 170px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06), inset 0 1px 2px rgba(255, 255, 255, 0.1);
}

.filter-controls select:hover,
select.modern-select:hover {
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.15), inset 0 1px 2px rgba(255, 255, 255, 0.1);
    transform: translateY(-1px);
}

.filter-controls select:focus,
select.modern-select:focus {
    outline: none;
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.2), 0 4px 12px rgba(0, 123, 255, 0.15);
}

/* Dark theme dropdown arrow */
[data-theme="dark"] .filter-controls select,
[data-theme="dark"] select.modern-select {
    background-image: 
        linear-gradient(135deg, transparent 50%, #64b5f6 50%),
        linear-gradient(225deg, transparent 50%, #64b5f6 50%);
    background-position: 
        calc(100% - 18px) calc(50% + 2px),
        calc(100% - 12px) calc(50% + 2px);
    background-size: 6px 6px, 6px 6px;
}

/* Modern Search Input in Filters */
.filter-controls input[type="text"],
.filter-controls input[type="search"],
input.modern-input {
    padding: 0.75rem 1rem 0.75rem 2.75rem;
    border: none;
    border-radius: 12px;
    background-color: var(--bg-color);
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='18' height='18' viewBox='0 0 24 24' fill='none' stroke='%23007bff' stroke-width='2.5' stroke-linecap='round'%3E%3Ccircle cx='11' cy='11' r='7'/%3E%3Cpath d='m21 21-4.35-4.35'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: 0.85rem center;
    color: var(--text-color);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.25s ease;
    min-width: 220px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06), inset 0 1px 2px rgba(255, 255, 255, 0.1);
}

.filter-controls input[type="text"]:hover,
.filter-controls input[type="search"]:hover,
input.modern-input:hover {
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.15), inset 0 1px 2px rgba(255, 255, 255, 0.1);
    transform: translateY(-1px);
}

.filter-controls input[type="text"]:focus,
.filter-controls input[type="search"]:focus,
input.modern-input:focus {
    outline: none;
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.2), 0 4px 12px rgba(0, 123, 255, 0.15);
}

.filter-controls input::placeholder {
    color: var(--secondary-color);
    font-weight: 400;
}

/* Filter Buttons */
.filter-controls button {
    padding: 0.75rem 1.25rem;
    border: none;
    border-radius: 12px;
    background: var(--bg-color);
    color: var(--text-color);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s ease;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

.filter-controls button:hover {
    background: linear-gradient(135deg, var(--primary-color), #0056b3);
    color: white;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.3);
}

/* Filter Label */
.filter-label {
    font-size: 0.8rem;
    font-weight: 700;
    color: var(--secondary-color);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    padding: 0 0.5rem;
}

/* Filter Divider */
.filter-divider {
    width: 1px;
    height: 28px;
    background: linear-gradient(180deg, transparent, var(--border-color), transparent);
    margin: 0 0.5rem;
}

.topics-list,
.questions-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.question-card {
    background-color: var(--card-bg);
    padding: 1.5rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
    transition: all 0.3s;
}

.question-card:hover {
    box-shadow: var(--shadow-lg);
}

.question-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    cursor: pointer;
}

.question-answer {
    margin-top: 1rem;
    padding: 1rem;
    background-color: var(--bg-color);
    border-left: 4px solid var(--primary-color);
    border-radius: 5px;
    display: none;
}

.question-answer.show {
    display: block;
}

.favorite-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--secondary-color);
    transition: color 0.3s;
}

.favorite-btn.active {
    color: var(--warning-color);
}

/* ==================== Modern Tabs ==================== */
.tabs {
    display: flex;
    gap: 0.5rem;
    margin: 2rem 0;
    padding: 0.35rem;
    background: var(--card-bg);
    border-radius: 12px;
    border: 1px solid var(--border-color);
    overflow-x: auto;
}

.tab-btn {
    padding: 0.75rem 1.5rem;
    background: transparent;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--secondary-color);
    transition: all 0.2s ease;
    white-space: nowrap;
}

.tab-btn:hover {
    color: var(--text-color);
    background: var(--bg-color);
}

.tab-btn.active {
    color: white;
    background: linear-gradient(135deg, var(--primary-color), #0056b3);
    box-shadow: 0 2px 8px rgba(0, 123, 255, 0.3);
}

.tab-content {
    display: none;
    padding: 2rem 0;
}

.tab-content.active {
    display: block;
}

/* ==================== Modern Button Styles ==================== */
.btn-primary,
.btn-secondary {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 600;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), #0056b3);
    color: white;
    box-shadow: 0 2px 8px rgba(0, 123, 255, 0.25);
}

.btn-primary:hover {
    background: linear-gradient(135deg, #0056b3, #004494);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.35);
}

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

.btn-secondary {
    background: var(--card-bg);
    color: var(--text-color);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    background: rgba(0, 123, 255, 0.05);
}

/* Small Button Variant */
.btn-small {
    padding: 0.4rem 0.85rem;
    font-size: 0.8rem;
    border-radius: 6px;
}

/* Icon Button */
.btn-icon {
    padding: 0.6rem;
    border-radius: 8px;
    width: 40px;
    height: 40px;
}

/* Success/Danger Button Variants */
.btn-success {
    background: linear-gradient(135deg, var(--success-color), #1e7e34);
    color: white;
    box-shadow: 0 2px 8px rgba(40, 167, 69, 0.25);
}

.btn-success:hover {
    background: linear-gradient(135deg, #1e7e34, #155d27);
    transform: translateY(-2px);
}

.btn-danger {
    background: linear-gradient(135deg, var(--danger-color), #c82333);
    color: white;
    box-shadow: 0 2px 8px rgba(220, 53, 69, 0.25);
}

.btn-danger:hover {
    background: linear-gradient(135deg, #c82333, #a71d2a);
    transform: translateY(-2px);
}

footer {
    text-align: center;
    padding: 2rem;
    margin-top: 4rem;
    background-color: var(--card-bg);
    border-top: 1px solid var(--border-color);
}

.error-message {
    color: var(--danger-color);
    margin-top: 1rem;
    padding: 1rem;
    background-color: rgba(220, 53, 69, 0.1);
    border-radius: 5px;
}

/* ==================== General Form Styles ==================== */
input[type="text"],
input[type="email"],
input[type="password"],
input[type="number"],
input[type="search"],
input[type="url"],
textarea,
select {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--bg-color);
    color: var(--text-color);
    font-size: 0.95rem;
    font-family: inherit;
    transition: all 0.2s ease;
}

input[type="text"]:hover,
input[type="email"]:hover,
input[type="password"]:hover,
input[type="number"]:hover,
input[type="search"]:hover,
input[type="url"]:hover,
textarea:hover,
select:hover {
    border-color: var(--primary-color);
}

input[type="text"]:focus,
input[type="email"]:focus,
input[type="password"]:focus,
input[type="number"]:focus,
input[type="search"]:focus,
input[type="url"]:focus,
textarea:focus,
select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.15);
}

input::placeholder,
textarea::placeholder {
    color: var(--secondary-color);
}

/* Form Group */
.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--text-color);
    font-size: 0.9rem;
}

/* Textarea specific */
textarea {
    resize: vertical;
    min-height: 100px;
}

/* Select styling */
select {
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;
    background-image: 
        linear-gradient(135deg, transparent 50%, var(--primary-color) 50%),
        linear-gradient(225deg, transparent 50%, var(--primary-color) 50%);
    background-position: 
        calc(100% - 18px) calc(50% + 2px),
        calc(100% - 12px) calc(50% + 2px);
    background-size: 6px 6px, 6px 6px;
    background-repeat: no-repeat;
    padding-right: 2.75rem;
    cursor: pointer;
    border-radius: 10px;
}

[data-theme="dark"] select {
    background-image: 
        linear-gradient(135deg, transparent 50%, #64b5f6 50%),
        linear-gradient(225deg, transparent 50%, #64b5f6 50%);
    background-position: 
        calc(100% - 18px) calc(50% + 2px),
        calc(100% - 12px) calc(50% + 2px);
    background-size: 6px 6px, 6px 6px;
}

.admin-section {
    max-width: 800px;
    margin: 2rem auto;
}

.admin-section form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.admin-section input {
    padding: 0.75rem 1rem;
}

.admin-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    margin: 2rem 0;
}

.admin-table {
    width: 100%;
    border-collapse: collapse;
    margin: 2rem 0;
}

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

.admin-table th {
    background-color: var(--card-bg);
    font-weight: bold;
}

/* ==================== Quiz Card Styles ==================== */
.quiz-card {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    margin-bottom: 2rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

.quiz-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.1rem;
}

.quiz-options {
    list-style: none;
    margin: 1.25rem 0;
}

.quiz-options li {
    padding: 1rem 1.25rem;
    margin: 0.6rem 0;
    background-color: var(--bg-color);
    border: 2px solid var(--border-color);
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-weight: 500;
}

.quiz-options li::before {
    content: '';
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    flex-shrink: 0;
    transition: all 0.2s ease;
}

.quiz-options li:hover {
    border-color: var(--primary-color);
    background-color: rgba(0, 123, 255, 0.05);
}

.quiz-options li:hover::before {
    border-color: var(--primary-color);
}

.quiz-options li.selected {
    border-color: var(--primary-color);
    background-color: rgba(0, 123, 255, 0.1);
}

.quiz-options li.selected::before {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    box-shadow: inset 0 0 0 3px var(--bg-color);
}

.quiz-options li.correct {
    border-color: var(--success-color);
    background: linear-gradient(135deg, rgba(40, 167, 69, 0.1), rgba(40, 167, 69, 0.05));
}

.quiz-options li.correct::before {
    background-color: var(--success-color);
    border-color: var(--success-color);
    box-shadow: inset 0 0 0 3px var(--bg-color);
}

.quiz-options li.incorrect {
    border-color: var(--danger-color);
    background: linear-gradient(135deg, rgba(220, 53, 69, 0.1), rgba(220, 53, 69, 0.05));
}

.quiz-options li.incorrect::before {
    background-color: var(--danger-color);
    border-color: var(--danger-color);
    box-shadow: inset 0 0 0 3px var(--bg-color);
}

@media (max-width: 768px) {
    /* Hide desktop menu, show hamburger */
    .nav-menu {
        display: none !important;
    }
    
    .menu-toggle {
        display: block;
    }
    
    .mobile-menu {
        display: flex;
    }
    
    /* Navbar adjustments */
    .navbar {
        position: relative;
    }
    
    .nav-container {
        padding: 0 1rem;
    }
    
    .nav-brand h1 {
        font-size: 1.2rem;
    }
    
    /* Hero section - smaller fonts */
    .hero-section {
        padding: 2rem 0;
    }
    
    .hero-section h1 {
        font-size: 1.6rem;
        line-height: 1.3;
    }
    
    .hero-section p {
        font-size: 0.95rem;
        margin-bottom: 1.5rem;
    }
    
    /* Search box */
    .search-box {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .search-box input {
        font-size: 0.9rem;
        padding: 0.9rem 1.25rem;
        text-align: left;
        width: 100%;
    }
    
    .search-box button {
        font-size: 0.9rem;
        padding: 0.9rem 1.5rem;
        width: 100%;
        justify-content: center;
    }
    
    /* Stats section */
    .stats-section {
        grid-template-columns: repeat(2, 1fr);
        gap: 0.75rem;
        margin: 2rem 0;
    }
    
    .stat-card {
        padding: 1rem;
    }
    
    .stat-card .stat-icon {
        font-size: 1.5rem;
        margin-bottom: 0.5rem;
    }
    
    .stat-card h3 {
        font-size: 1.5rem;
        margin-bottom: 0.25rem;
    }
    
    .stat-card p {
        font-size: 0.75rem;
    }
    
    .stat-card .stat-link {
        font-size: 0.7rem;
    }
    
    /* Section headers */
    .categories-section h2,
    .featured-section h2 {
        font-size: 1.2rem;
        margin-bottom: 1rem;
    }
    
    /* Category grid */
    .category-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 0.75rem;
    }
    
    .category-card-compact {
        padding: 0.75rem 0.85rem;
        min-height: 75px;
        gap: 0.3rem;
    }
    
    .category-card-compact .category-name {
        font-size: 0.8rem;
    }
    
    .category-card-compact .category-topic-count {
        font-size: 0.7rem;
    }
    
    .level-chip {
        font-size: 0.6rem;
        padding: 0.15rem 0.5rem;
    }
    
    /* Topics grid */
    .topics-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    .topic-card {
        padding: 1rem;
    }
    
    .topic-card h3 {
        font-size: 1rem;
    }
    
    .topic-card p {
        font-size: 0.85rem;
    }
    
    /* Filter controls */
    .filter-controls {
        flex-direction: column;
        padding: 1rem;
        gap: 0.65rem;
        border-radius: 12px;
    }
    
    .filter-controls select,
    .filter-controls input[type="text"],
    .filter-controls input[type="search"] {
        width: 100%;
        min-width: unset;
        padding: 0.85rem 1rem;
        padding-right: 2.5rem;
        border-radius: 10px;
    }
    
    .filter-controls input[type="text"],
    .filter-controls input[type="search"] {
        padding-left: 2.5rem;
    }
    
    .filter-controls button {
        width: 100%;
        justify-content: center;
        padding: 0.85rem 1rem;
        border-radius: 10px;
    }
    
    .filter-divider {
        display: none;
    }
    
    .page-header h1 {
        font-size: 1.5rem;
    }
    
    .page-header h1::before {
        width: 3px;
    }
    
    /* Tabs mobile */
    .tabs {
        gap: 0.25rem;
        padding: 0.25rem;
    }
    
    .tab-btn {
        padding: 0.6rem 1rem;
        font-size: 0.8rem;
    }
    
    /* Quiz options mobile */
    .quiz-options li {
        padding: 0.85rem 1rem;
        font-size: 0.9rem;
    }
    
    .quiz-options li::before {
        width: 18px;
        height: 18px;
    }
    
    /* Container padding */
    .container {
        padding: 1rem;
    }
    
    /* Footer */
    footer {
        padding: 1.5rem 1rem;
        margin-top: 2rem;
        font-size: 0.85rem;
    }
}

@media (max-width: 480px) {
    .hero-section h1 {
        font-size: 1.4rem;
    }
    
    .hero-section p {
        font-size: 0.85rem;
    }
    
    .stat-card h3 {
        font-size: 1.3rem;
    }
    
    .stat-card p {
        font-size: 0.7rem;
    }
    
    .category-card-compact .category-name {
        font-size: 0.75rem;
    }
}

/* Topic Ordering & Navigation - Mobile Styles */
@media (max-width: 768px) {
    .topic-order-badge {
        min-width: 30px;
        height: 30px;
        font-size: 0.8rem;
    }
    
    .topic-card-ordered {
        gap: 0.75rem;
    }
    
    .category-group-title {
        font-size: 1.1rem;
    }
    
    .topic-breadcrumb {
        font-size: 0.8rem;
    }
    
    .topic-position-badge,
    .category-tag,
    .badge {
        font-size: 0.65rem;
        padding: 0.2rem 0.5rem;
    }
    
    .topic-position-badge::before,
    .category-tag::before {
        font-size: 0.6rem;
    }
    
    .topic-navigation {
        padding: 1.25rem;
        margin-top: 2rem;
    }
    
    .topic-nav-title {
        font-size: 1rem;
        margin-bottom: 1rem;
    }
    
    .topic-nav-links {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }
    
    .topic-nav-prev,
    .topic-nav-next {
        text-align: center;
    }
    
    .topic-nav-link {
        padding: 1rem;
    }
    
    .nav-topic-title {
        font-size: 0.9rem;
    }
    
    .nav-direction {
        font-size: 0.8rem;
    }
    
    .nav-topic-order {
        font-size: 0.75rem;
    }
    
    .topic-nav-placeholder {
        display: none;
    }
}