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

:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --accent-color: #3b82f6;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --background: #ffffff;
    --surface: #f9fafb;
    --border: #e5e7eb;
    --shadow: rgba(0, 0, 0, 0.1);
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    --border-radius: 8px;
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--background);
}

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

/* Navigation */
.navbar {
    background: var(--background);
    box-shadow: 0 2px 10px var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 700;
    font-size: 1.25rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 30px;
}

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: var(--transition);
    padding: 8px 16px;
    border-radius: var(--border-radius);
}

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

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 4px;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    transition: var(--transition);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 12px 24px;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 600;
    text-align: center;
    transition: var(--transition);
    border: 2px solid transparent;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--secondary-color);
    transform: translateY(-2px);
}

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border-color: var(--primary-color);
}

.btn-secondary:hover {
    background: var(--primary-color);
    color: white;
}

.btn-outline {
    background: transparent;
    color: var(--text-primary);
    border-color: var(--border);
}

.btn-outline:hover {
    background: var(--surface);
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* Hero Section */
.hero {
    padding: 80px 0;
    background: linear-gradient(135deg, var(--surface) 0%, var(--background) 100%);
    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: 60px;
    align-items: center;
}

.hero-content h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 20px;
    color: var(--text-primary);
    line-height: 1.2;
}

.hero-content p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 30px;
}

.hero-buttons {
    display: flex;
    gap: 20px;
}

.hero-image img {
    width: 100%;
    height: auto;
    border-radius: var(--border-radius);
}

/* Video Grid */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
    margin-bottom: 40px;
}

.video-card {
    background: var(--background);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: 0 4px 20px var(--shadow);
    transition: var(--transition);
    text-decoration: none;
    color: inherit;
}

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

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

.video-info {
    padding: 20px;
}

.video-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 8px;
    line-height: 1.4;
}

.video-channel {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 8px;
}

.video-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.video-description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

.video-category {
    display: inline-block;
    background: var(--surface);
    color: var(--primary-color);
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
    margin-top: 10px;
}

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

.featured-videos h2,
.categories-preview h2 {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 50px;
    color: var(--text-primary);
}

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

/* Category Grid */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.category-card {
    background: var(--background);
    padding: 40px 30px;
    border-radius: var(--border-radius);
    text-align: center;
    box-shadow: 0 4px 20px var(--shadow);
    transition: var(--transition);
    text-decoration: none;
    color: inherit;
    border: 2px solid transparent;
}

.category-card:hover {
    transform: translateY(-5px);
    border-color: var(--primary-color);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.15);
}

.category-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 15px;
    color: var(--text-primary);
}

.category-card p {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Search and Filter */
.search-filter {
    background: var(--surface);
    padding: 40px 0;
    margin-bottom: 40px;
}

.search-container {
    display: flex;
    gap: 20px;
    align-items: center;
    flex-wrap: wrap;
}

.search-input {
    flex: 1;
    min-width: 300px;
    padding: 12px 16px;
    border: 2px solid var(--border);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: var(--transition);
}

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

.filter-select {
    padding: 12px 16px;
    border: 2px solid var(--border);
    border-radius: var(--border-radius);
    font-size: 1rem;
    background: var(--background);
    cursor: pointer;
    transition: var(--transition);
}

.filter-select:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Video Detail */
.video-detail {
    padding: 40px 0;
}

.video-player {
    margin-bottom: 30px;
}

.video-embed {
    width: 100%;
    height: 500px;
    border: none;
    border-radius: var(--border-radius);
}

.video-detail-info h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 15px;
}

.video-detail-meta {
    display: flex;
    gap: 30px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.video-detail-meta span {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.video-topics {
    margin: 20px 0;
}

.video-topics h3 {
    margin-bottom: 10px;
    font-size: 1.1rem;
}

.topic-tag {
    display: inline-block;
    background: var(--surface);
    color: var(--primary-color);
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.85rem;
    margin: 4px 8px 4px 0;
    font-weight: 500;
}

.content-disclaimer {
    background: var(--surface);
    padding: 20px;
    border-radius: var(--border-radius);
    margin: 30px 0;
    border-left: 4px solid var(--primary-color);
}

.content-disclaimer p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin: 0;
}

/* Forms */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-primary);
}

.form-input,
.form-textarea {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border);
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-family: inherit;
    transition: var(--transition);
}

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

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

/* Footer */
footer {
    background: var(--text-primary);
    color: white;
    padding: 60px 0 20px;
    margin-top: 80px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 40px;
    margin-bottom: 40px;
}

.footer-section h3,
.footer-section h4 {
    margin-bottom: 20px;
    font-weight: 600;
}

.footer-section p {
    color: #d1d5db;
    line-height: 1.6;
}

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

.footer-section ul li {
    margin-bottom: 8px;
}

.footer-section ul li a {
    color: #d1d5db;
    text-decoration: none;
    transition: var(--transition);
}

.footer-section ul li a:hover {
    color: white;
}

.footer-bottom {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid #374151;
    color: #9ca3af;
}

/* Page Content */
.page-content {
    padding: 40px 0;
    min-height: 60vh;
}

.page-content h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 30px;
    text-align: center;
}

.page-content h2 {
    font-size: 1.8rem;
    font-weight: 600;
    margin: 30px 0 15px;
    color: var(--text-primary);
}

.page-content p {
    margin-bottom: 15px;
    line-height: 1.7;
    color: var(--text-secondary);
}

.page-content ul,
.page-content ol {
    margin: 15px 0;
    padding-left: 30px;
}

.page-content li {
    margin-bottom: 8px;
    line-height: 1.6;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--background);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: 0 10px 27px var(--shadow);
        padding: 20px 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .hamburger {
        display: flex;
    }

    .hamburger.active span:nth-child(2) {
        opacity: 0;
    }

    .hamburger.active span:nth-child(1) {
        transform: translateY(7px) rotate(45deg);
    }

    .hamburger.active span:nth-child(3) {
        transform: translateY(-7px) rotate(-45deg);
    }

    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 40px;
    }

    .hero-content h1 {
        font-size: 2.5rem;
    }

    .hero-buttons {
        justify-content: center;
    }

    .video-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .search-container {
        flex-direction: column;
        align-items: stretch;
    }

    .search-input {
        min-width: 100%;
    }

    .video-embed {
        height: 300px;
    }

    .video-detail-meta {
        flex-direction: column;
        gap: 10px;
    }

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

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

    .hero {
        padding: 40px 0;
    }

    .hero-content h1 {
        font-size: 2rem;
    }

    .featured-videos,
    .categories-preview {
        padding: 40px 0;
    }

    .featured-videos h2,
    .categories-preview h2 {
        font-size: 2rem;
    }

    .video-card {
        margin-bottom: 20px;
    }

    .btn {
        padding: 10px 20px;
        font-size: 0.9rem;
    }
}

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

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

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

.mb-20 {
    margin-bottom: 20px;
}

.mb-30 {
    margin-bottom: 30px;
}

.mt-20 {
    margin-top: 20px;
}

.mt-30 {
    margin-top: 30px;
}

.hidden {
    display: none;
}

.loading {
    opacity: 0.6;
    pointer-events: none;
}