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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fff;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.header {
    background: #fff;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 20px;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo {
    width: 40px;
    height: 40px;
}

.nav-brand h1 {
    font-size: 1.5rem;
    color: #2c3e50;
    font-weight: 600;
}

.nav {
    display: flex;
    gap: 2rem;
}

.nav-link {
    text-decoration: none;
    color: #666;
    font-weight: 500;
    transition: color 0.3s;
}

.nav-link:hover,
.nav-link.active {
    color: #3498db;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

.hero-content h2 {
    font-size: 3rem;
    margin-bottom: 1rem;
    font-weight: 700;
}

.hero-content p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

/* Buttons */
.btn-primary,
.btn-secondary {
    display: inline-block;
    padding: 12px 30px;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: #3498db;
    color: white;
}

.btn-primary:hover {
    background: #2980b9;
    transform: translateY(-2px);
}

.btn-secondary {
    background: transparent;
    color: #3498db;
    border: 2px solid #3498db;
}

.btn-secondary:hover {
    background: #3498db;
    color: white;
}

/* Video Grid */
.featured-videos,
.all-videos {
    padding: 4rem 0;
}

.featured-videos h2,
.all-videos h2 {
    text-align: center;
    margin-bottom: 3rem;
    font-size: 2.5rem;
    color: #2c3e50;
}

.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.video-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
}

.video-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 30px rgba(0,0,0,0.15);
}

.video-card a {
    text-decoration: none;
    color: inherit;
    display: block;
}

.video-card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

.video-info {
    padding: 1.5rem;
}

.video-info h3 {
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
    color: #2c3e50;
    line-height: 1.4;
}

.video-creator {
    color: #666;
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.video-meta {
    display: flex;
    gap: 1rem;
    font-size: 0.8rem;
    color: #888;
}

.category {
    background: #e8f4f8;
    color: #3498db;
    padding: 2px 8px;
    border-radius: 12px;
    font-weight: 500;
}

/* Categories */
.categories-preview {
    background: #f8f9fa;
    padding: 4rem 0;
}

.categories-preview h2 {
    text-align: center;
    margin-bottom: 3rem;
    font-size: 2.5rem;
    color: #2c3e50;
}

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

.category-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    text-align: center;
    text-decoration: none;
    color: inherit;
    transition: transform 0.3s, box-shadow 0.3s;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.category-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.1);
}

.category-card h3 {
    color: #3498db;
    margin-bottom: 0.5rem;
    font-size: 1.3rem;
}

.category-card p {
    color: #666;
    font-size: 0.9rem;
}

/* Search and Filters */
.search-filters {
    background: #f8f9fa;
    padding: 2rem 0;
    border-bottom: 1px solid #eee;
}

.search-bar {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.search-input {
    flex: 1;
    min-width: 300px;
    padding: 12px;
    border: 2px solid #ddd;
    border-radius: 6px;
    font-size: 1rem;
}

.search-input:focus {
    outline: none;
    border-color: #3498db;
}

.filter-buttons {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 8px 16px;
    background: white;
    border: 2px solid #ddd;
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s;
    font-size: 0.9rem;
}

.filter-btn:hover,
.filter-btn.active {
    background: #3498db;
    color: white;
    border-color: #3498db;
}

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

.video-embed {
    max-width: 800px;
    margin: 0 auto 2rem;
}

.embed-placeholder {
    width: 100%;
    height: 450px;
    background: #f0f0f0;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #666;
    font-size: 1.1rem;
}

.video-details {
    max-width: 800px;
    margin: 0 auto;
}

.video-details h1 {
    font-size: 2rem;
    margin-bottom: 1rem;
    color: #2c3e50;
}

.video-meta-detail {
    display: flex;
    gap: 2rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    color: #666;
}

.topics {
    margin: 1.5rem 0;
}

.topics h3 {
    margin-bottom: 0.5rem;
    color: #2c3e50;
}

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

.topic-tag {
    background: #e8f4f8;
    color: #3498db;
    padding: 4px 12px;
    border-radius: 16px;
    font-size: 0.8rem;
    font-weight: 500;
}

.content-notice {
    background: #e8f4f8;
    border-left: 4px solid #3498db;
    padding: 1rem;
    margin: 2rem 0;
    border-radius: 4px;
}

/* Footer */
.footer {
    background: #2c3e50;
    color: white;
    padding: 3rem 0 1rem;
}

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

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
    color: #3498db;
}

.footer-section ul {
    list-style: none;
}

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

.footer-section a {
    color: #bbb;
    text-decoration: none;
    transition: color 0.3s;
}

.footer-section a:hover {
    color: #3498db;
}

.footer-bottom {
    border-top: 1px solid #34495e;
    padding-top: 1rem;
    text-align: center;
    color: #bbb;
}

/* Utility Classes */
.text-center {
    text-align: center;
}

.mt-2 { margin-top: 2rem; }
.mb-2 { margin-bottom: 2rem; }

/* Responsive */
@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        gap: 1rem;
    }
    
    .nav {
        gap: 1rem;
    }
    
    .hero-content h2 {
        font-size: 2rem;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .search-bar {
        flex-direction: column;
    }
    
    .search-input {
        min-width: auto;
    }
    
    .video-meta-detail {
        flex-direction: column;
        gap: 0.5rem;
    }
}

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

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: #2c3e50;
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 12px;
    border: 2px solid #ddd;
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: #3498db;
}

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

/* Content Pages */
.content-page {
    padding: 3rem 0;
    max-width: 800px;
    margin: 0 auto;
}

.content-page h1 {
    font-size: 2.5rem;
    margin-bottom: 2rem;
    color: #2c3e50;
}

.content-page h2 {
    font-size: 1.8rem;
    margin: 2rem 0 1rem;
    color: #2c3e50;
}

.content-page h3 {
    font-size: 1.4rem;
    margin: 1.5rem 0 0.5rem;
    color: #2c3e50;
}

.content-page p {
    margin-bottom: 1rem;
    line-height: 1.7;
}

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

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