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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 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;
}

.nav {
    padding: 1rem 0;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: #2563eb;
    font-weight: bold;
    font-size: 1.2rem;
}

.logo img {
    margin-right: 10px;
}

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

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

.nav-link:hover,
.nav-link.active {
    color: #2563eb;
}

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

.nav-toggle span {
    width: 25px;
    height: 3px;
    background: #333;
    margin: 3px 0;
    transition: 0.3s;
}

/* Hero Section */
.hero {
    padding: 80px 0;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    display: flex;
    align-items: center;
    min-height: 500px;
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    line-height: 1.2;
}

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

.cta-button {
    display: inline-block;
    background: #fff;
    color: #2563eb;
    padding: 15px 30px;
    text-decoration: none;
    border-radius: 8px;
    font-weight: 600;
    transition: transform 0.3s;
}

.cta-button:hover {
    transform: translateY(-2px);
}

/* Sections */
.featured-section,
.categories-section {
    padding: 80px 0;
}

.categories-section {
    background: #f8fafc;
}

section h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: #1e293b;
}

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

.video-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
    text-decoration: none;
    color: inherit;
}

.video-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
}

.video-thumbnail {
    position: relative;
    width: 100%;
    height: 200px;
    overflow: hidden;
}

.video-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-duration {
    position: absolute;
    bottom: 10px;
    right: 10px;
    background: rgba(0,0,0,0.8);
    color: white;
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 0.8rem;
}

.video-info {
    padding: 1.5rem;
}

.video-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.video-creator {
    color: #666;
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.video-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.8rem;
    color: #999;
}

.video-category {
    background: #e0f2fe;
    color: #0277bd;
    padding: 2px 8px;
    border-radius: 12px;
}

/* Categories Grid */
.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.category-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s;
    text-decoration: none;
    color: inherit;
}

.category-card:hover {
    transform: translateY(-3px);
}

.category-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto 1rem;
    background: #2563eb;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: white;
}

.category-name {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

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

/* Buttons */
.btn-secondary {
    display: inline-block;
    background: #2563eb;
    color: white;
    padding: 12px 24px;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 500;
    transition: background 0.3s;
}

.btn-secondary:hover {
    background: #1d4ed8;
}

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

/* Search and Filters */
.search-section {
    background: #f8fafc;
    padding: 2rem 0;
}

.search-container {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.search-input {
    flex: 1;
    min-width: 300px;
    padding: 12px 16px;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    font-size: 1rem;
}

.search-input:focus {
    outline: none;
    border-color: #2563eb;
}

.filter-select {
    padding: 12px 16px;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    background: white;
    font-size: 1rem;
    min-width: 150px;
}

.filter-select:focus {
    outline: none;
    border-color: #2563eb;
}

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

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

.video-embed {
    position: relative;
    width: 100%;
    height: 0;
    padding-bottom: 56.25%;
    border-radius: 12px;
    overflow: hidden;
}

.video-embed iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.video-details {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 3rem;
}

.video-main h1 {
    font-size: 2rem;
    margin-bottom: 1rem;
}

.video-description {
    line-height: 1.8;
    margin-bottom: 2rem;
}

.video-sidebar {
    background: #f8fafc;
    padding: 2rem;
    border-radius: 12px;
    height: fit-content;
}

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

.stat-item {
    display: flex;
    justify-content: space-between;
    margin-bottom: 0.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid #e2e8f0;
}

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

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

.topic-tag {
    background: #e0f2fe;
    color: #0277bd;
    padding: 4px 12px;
    border-radius: 16px;
    font-size: 0.8rem;
}

.content-notice {
    background: #fff3cd;
    border: 1px solid #ffeaa7;
    padding: 1rem;
    border-radius: 8px;
    font-size: 0.9rem;
    color: #856404;
}

/* Footer */
.footer {
    background: #1e293b;
    color: white;
    padding: 3rem 0 1rem;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
    color: #f1f5f9;
}

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

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

.footer-section a {
    color: #cbd5e1;
    text-decoration: none;
    transition: color 0.3s;
}

.footer-section a:hover {
    color: #f1f5f9;
}

.footer-bottom {
    border-top: 1px solid #374151;
    margin-top: 2rem;
    padding-top: 1rem;
    text-align: center;
    color: #94a3b8;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .video-details {
        grid-template-columns: 1fr;
    }
    
    .search-container {
        flex-direction: column;
    }
    
    .search-input {
        min-width: auto;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 40px 0;
    }
    
    .hero h1 {
        font-size: 1.5rem;
    }
    
    .hero p {
        font-size: 1rem;
    }
    
    .featured-section,
    .categories-section {
        padding: 40px 0;
    }
    
    section h2 {
        font-size: 2rem;
    }
}

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

.form-label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: #374151;
}

.form-input,
.form-textarea {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-input:focus,
.form-textarea:focus {
    outline: none;
    border-color: #2563eb;
}

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

.form-button {
    background: #2563eb;
    color: white;
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background 0.3s;
}

.form-button:hover {
    background: #1d4ed8;
}

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

.page-content h1 {
    font-size: 2.5rem;
    margin-bottom: 2rem;
    color: #1e293b;
}

.page-content h2 {
    font-size: 1.8rem;
    margin: 2rem 0 1rem;
    color: #374151;
}

.page-content p {
    margin-bottom: 1rem;
    line-height: 1.8;
}

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

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