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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #f59e0b;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --border-radius: 8px;
    --border-radius-lg: 12px;
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

body {
    font-family: var(--font-family);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

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

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.nav-logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 600;
    font-size: 1.25rem;
}

.logo-img {
    width: 32px;
    height: 32px;
    margin-right: 8px;
}

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

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.2s;
}

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

.nav-toggle {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}

.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    margin: 2px 0;
    transition: 0.3s;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
    padding: 4rem 1rem;
    display: flex;
    align-items: center;
    min-height: 500px;
    position: relative;
    overflow: hidden;
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
    z-index: 2;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.5;
}

.hero-btn {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 12px 24px;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 600;
    transition: background-color 0.2s;
}

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

.hero-bg {
    display: flex;
    justify-content: center;
    align-items: center;
}

.hero-img {
    width: 100%;
    max-width: 400px;
    height: auto;
}

/* Sections */
.featured,
.categories-preview {
    padding: 4rem 0;
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 3rem;
    color: var(--text-primary);
}

/* Video Grid */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.video-card {
    background: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: transform 0.2s, box-shadow 0.2s;
    text-decoration: none;
    color: inherit;
}

.video-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.video-thumbnail {
    width: 100%;
    height: 200px;
    object-fit: cover;
    background: var(--bg-tertiary);
}

.video-info {
    padding: 1.5rem;
}

.video-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.video-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.video-channel {
    font-weight: 500;
}

.video-duration {
    background: var(--bg-tertiary);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.75rem;
}

.video-desc {
    color: var(--text-secondary);
    font-size: 0.875rem;
    line-height: 1.5;
}

.video-category {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 0.75rem;
    font-weight: 500;
    margin-top: 0.75rem;
}

/* Category Grid */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
}

.category-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 2rem 1.5rem;
    text-align: center;
    text-decoration: none;
    color: inherit;
    transition: transform 0.2s, box-shadow 0.2s;
}

.category-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.category-name {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.category-count {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* Buttons */
.view-all-btn {
    display: inline-block;
    background: var(--bg-tertiary);
    color: var(--text-primary);
    padding: 12px 24px;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 600;
    transition: background-color 0.2s;
    border: 1px solid var(--border-color);
}

.view-all-btn:hover {
    background: var(--border-color);
}

.section-footer {
    text-align: center;
}

/* Search and Filters */
.search-section {
    background: var(--bg-secondary);
    padding: 2rem 0;
    margin-bottom: 2rem;
}

.search-container {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.search-input {
    flex: 1;
    min-width: 250px;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

.filter-select {
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--bg-primary);
    font-size: 1rem;
    min-width: 150px;
}

.search-btn {
    padding: 12px 24px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s;
}

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

/* Video Detail Page */
.video-detail {
    padding: 2rem 0;
}

.video-player {
    margin-bottom: 2rem;
}

.video-embed {
    width: 100%;
    height: 400px;
    border: none;
    border-radius: var(--border-radius);
}

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

.video-detail-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 1rem;
    line-height: 1.3;
}

.video-detail-meta {
    display: flex;
    gap: 2rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
}

.video-detail-desc {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 2rem;
}

.video-topics {
    margin-bottom: 2rem;
}

.topics-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 0.5rem;
}

.topic-tag {
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 0.875rem;
}

.content-notice {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1rem;
    margin: 2rem 0;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Forms */
.form-group {
    margin-bottom: 1.5rem;
}

.form-label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-input,
.form-textarea {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-family: inherit;
}

.form-textarea {
    min-height: 120px;
    resize: vertical;
}

.form-input:focus,
.form-textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgb(37 99 235 / 0.1);
}

.form-btn {
    background: var(--primary-color);
    color: white;
    padding: 12px 24px;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s;
}

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

/* Footer */
.footer {
    background: var(--text-primary);
    color: white;
    padding: 3rem 0 1rem;
    margin-top: 4rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.footer-heading {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: #e2e8f0;
}

.footer-desc {
    color: #94a3b8;
    line-height: 1.6;
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 0.5rem;
}

.footer-links a {
    color: #94a3b8;
    text-decoration: none;
    transition: color 0.2s;
}

.footer-links a:hover {
    color: white;
}

.footer-contact {
    color: #94a3b8;
    margin-bottom: 0.5rem;
    line-height: 1.5;
}

.footer-contact a {
    color: #94a3b8;
    text-decoration: none;
    transition: color 0.2s;
}

.footer-contact a:hover {
    color: white;
}

.footer-bottom {
    border-top: 1px solid #374151;
    padding-top: 1rem;
    text-align: center;
    color: #94a3b8;
    font-size: 0.875rem;
}

.disclaimer-text {
    margin-top: 0.5rem;
    font-size: 0.75rem;
    opacity: 0.8;
}

/* Content Pages */
.content-page {
    padding: 2rem 0;
    max-width: 800px;
    margin: 0 auto;
}

.content-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.content-section {
    margin-bottom: 2rem;
}

.content-section h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.content-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.content-section p {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 1rem;
}

.content-section ul {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 1rem;
    padding-left: 1.5rem;
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-subtitle {
        font-size: 1rem;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .search-container {
        flex-direction: column;
    }
    
    .search-input,
    .filter-select {
        min-width: 100%;
    }
    
    .video-detail-meta {
        flex-direction: column;
        gap: 1rem;
    }
    
    .video-embed {
        height: 250px;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 0.75rem;
    }
    
    .hero {
        padding: 2rem 1rem;
    }
    
    .hero-title {
        font-size: 1.75rem;
    }
    
    .section-title {
        font-size: 1.5rem;
    }
    
    .video-info {
        padding: 1rem;
    }
    
    .category-card {
        padding: 1.5rem 1rem;
    }
}