* {
    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: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: #333;
}

.logo {
    width: 32px;
    height: 32px;
}

.brand-name {
    font-size: 1.25rem;
    font-weight: bold;
    color: #2563eb;
}

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

.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;
    padding: 0.5rem;
}

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

/* Main */
.main {
    margin-top: 80px;
}

/* Hero */
.hero {
    display: flex;
    align-items: center;
    min-height: 500px;
    padding: 4rem 2rem;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.hero-content {
    flex: 1;
    max-width: 600px;
}

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

.hero-subtitle {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.hero-image {
    flex: 1;
    text-align: center;
}

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

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 0.5rem;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
    text-align: center;
}

.btn-primary {
    background: #fff;
    color: #2563eb;
}

.btn-primary:hover {
    background: #f8fafc;
    transform: translateY(-2px);
}

.btn-secondary {
    background: #2563eb;
    color: white;
}

.btn-secondary:hover {
    background: #1d4ed8;
    transform: translateY(-2px);
}

/* Sections */
.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 3rem;
    color: #1f2937;
}

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

.categories-preview {
    background: #f8fafc;
}

/* 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: 0.75rem;
    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(-4px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
}

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

.video-info {
    padding: 1.5rem;
}

.video-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    line-height: 1.3;
}

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

.video-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    font-size: 0.85rem;
    color: #888;
}

.video-description {
    color: #666;
    font-size: 0.9rem;
    line-height: 1.5;
}

.video-category {
    background: #e5e7eb;
    color: #374151;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.8rem;
    font-weight: 500;
}

/* 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: 0.75rem;
    text-align: center;
    text-decoration: none;
    color: inherit;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
}

.category-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
}

.category-card h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
    color: #2563eb;
}

.category-card p {
    color: #666;
}

/* Search and Filter */
.search-filter {
    background: #f8fafc;
    padding: 2rem 0;
    margin-bottom: 2rem;
}

.search-form {
    display: flex;
    gap: 1rem;
    max-width: 800px;
    margin: 0 auto;
    flex-wrap: wrap;
}

.search-input,
.filter-select {
    flex: 1;
    min-width: 200px;
    padding: 0.75rem;
    border: 1px solid #d1d5db;
    border-radius: 0.5rem;
    font-size: 1rem;
}

.search-input:focus,
.filter-select:focus {
    outline: none;
    border-color: #2563eb;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

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

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

.video-embed {
    width: 100%;
    height: 500px;
    border: none;
    border-radius: 0.5rem;
}

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

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

.video-stats {
    display: flex;
    gap: 2rem;
    margin-bottom: 1rem;
    font-size: 0.9rem;
    color: #666;
}

.video-topics {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.topic-tag {
    background: #e5e7eb;
    color: #374151;
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.8rem;
}

.video-description-full {
    background: #f8fafc;
    padding: 2rem;
    border-radius: 0.75rem;
    line-height: 1.6;
}

/* Footer */
.footer {
    background: #1f2937;
    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: #f9fafb;
}

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

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

.footer-section a {
    color: #d1d5db;
    text-decoration: none;
    transition: color 0.3s;
}

.footer-section a:hover {
    color: #f9fafb;
}

.footer-bottom {
    border-top: 1px solid #374151;
    padding-top: 2rem;
    text-align: center;
    color: #9ca3af;
}

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

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

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 1rem;
        box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    }

    .nav-menu.active {
        display: flex;
    }

    .nav-toggle {
        display: flex;
    }

    .hero {
        flex-direction: column;
        text-align: center;
        padding: 2rem 1rem;
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .section-title {
        font-size: 2rem;
    }

    .video-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }

    .categories-grid {
        grid-template-columns: 1fr;
    }

    .search-form {
        flex-direction: column;
    }

    .video-embed {
        height: 300px;
    }

    .video-stats {
        flex-direction: column;
        gap: 0.5rem;
    }

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }

    .nav {
        padding: 1rem 15px;
    }

    .hero-title {
        font-size: 1.75rem;
    }

    .video-card {
        margin: 0 -5px;
    }
}