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

:root {
    --primary-color: #2563eb;
    --secondary-color: #64748b;
    --accent-color: #059669;
    --background-color: #ffffff;
    --surface-color: #f8fafc;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --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);
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
}

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-color);
}

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

/* Header */
.header {
    background: var(--background-color);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 700;
    font-size: 1.25rem;
}

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

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.2s;
    padding: 0.5rem 0;
}

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

.nav-toggle {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

.nav-toggle span {
    width: 1.5rem;
    height: 2px;
    background: var(--text-primary);
    margin: 2px 0;
    transition: 0.3s;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    text-decoration: none;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all 0.2s;
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

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

.btn-primary:hover {
    background: #1d4ed8;
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--surface-color);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

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

.btn-outline {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

/* Hero Section */
.hero {
    padding: 4rem 1rem;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    min-height: 500px;
}

.hero-content h1 {
    font-size: 3rem;
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.hero-content p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.6;
}

.hero-actions {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

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

/* Video Grid */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
}

.video-card {
    background: var(--background-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s;
    border: 1px solid var(--border-color);
}

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

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

.video-thumbnail {
    position: relative;
    aspect-ratio: 16/9;
    overflow: hidden;
}

.video-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s;
}

.video-card:hover .video-thumbnail img {
    transform: scale(1.05);
}

.video-duration {
    position: absolute;
    bottom: 0.5rem;
    right: 0.5rem;
    background: rgba(0, 0, 0, 0.8);
    color: white;
    padding: 0.25rem 0.5rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
}

.video-info {
    padding: 1.5rem;
}

.video-info h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.video-channel {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-bottom: 0.75rem;
}

.video-description {
    color: var(--text-muted);
    font-size: 0.875rem;
    line-height: 1.5;
    margin-bottom: 1rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.video-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.875rem;
}

.video-views {
    color: var(--text-muted);
}

.video-category {
    background: var(--surface-color);
    color: var(--primary-color);
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-weight: 500;
}

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

.featured {
    background: var(--surface-color);
}

.featured h2,
.categories-preview h2 {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 3rem;
    color: var(--text-primary);
}

.section-footer {
    text-align: center;
    margin-top: 3rem;
}

/* Category Grid */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
}

.category-card {
    background: var(--background-color);
    padding: 2rem;
    border-radius: var(--radius-lg);
    text-align: center;
    text-decoration: none;
    color: inherit;
    border: 1px solid var(--border-color);
    transition: all 0.3s;
}

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

.category-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.category-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

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

/* Search and Filters */
.search-section {
    background: var(--surface-color);
    padding: 2rem 0;
    border-bottom: 1px solid var(--border-color);
}

.search-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 1rem;
}

.search-box {
    position: relative;
    margin-bottom: 2rem;
}

.search-input {
    width: 100%;
    padding: 1rem 1rem 1rem 3rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--background-color);
    transition: border-color 0.2s;
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.search-icon {
    position: absolute;
    left: 1rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    font-size: 1.25rem;
}

.filters {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    justify-content: center;
}

.filter-select {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--background-color);
    font-size: 0.875rem;
    cursor: pointer;
}

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

/* Video Details */
.video-header {
    padding: 2rem 0;
    border-bottom: 1px solid var(--border-color);
}

.video-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    line-height: 1.3;
}

.video-details {
    display: flex;
    gap: 2rem;
    flex-wrap: wrap;
    align-items: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.video-embed {
    padding: 2rem 0;
}

.embed-container {
    position: relative;
    width: 100%;
    height: 0;
    padding-bottom: 56.25%;
    background: var(--surface-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.embed-placeholder {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
    color: var(--text-secondary);
}

.video-content {
    padding: 2rem 0;
}

.video-description-full {
    font-size: 1rem;
    line-height: 1.6;
    color: var(--text-primary);
    margin-bottom: 2rem;
}

.video-topics {
    margin: 2rem 0;
}

.video-topics h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

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

.topic-tag {
    background: var(--surface-color);
    color: var(--text-primary);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    border: 1px solid var(--border-color);
}

/* Footer */
.footer {
    background: var(--text-primary);
    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;
    font-weight: 600;
}

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

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

.footer-section a {
    color: #cbd5e1;
    text-decoration: none;
    transition: color 0.2s;
}

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

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

/* Content Pages */
.page-header {
    background: var(--surface-color);
    padding: 3rem 0;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.page-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.page-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

.page-content {
    padding: 3rem 0;
}

.content-section {
    margin-bottom: 3rem;
}

.content-section h2 {
    font-size: 1.875rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.content-section h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.content-section p {
    margin-bottom: 1rem;
    line-height: 1.7;
    color: var(--text-primary);
}

.content-section ul,
.content-section ol {
    margin-bottom: 1rem;
    padding-left: 2rem;
    color: var(--text-primary);
}

.content-section li {
    margin-bottom: 0.5rem;
    line-height: 1.6;
}

/* Contact Form */
.contact-form {
    background: var(--surface-color);
    padding: 2rem;
    border-radius: var(--radius-lg);
    margin: 2rem 0;
}

.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: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--background-color);
    transition: border-color 0.2s;
}

.form-input:focus,
.form-textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 100%;
        left: 0;
        width: 100%;
        background: var(--background-color);
        flex-direction: column;
        padding: 2rem;
        box-shadow: var(--shadow-lg);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all 0.3s;
    }

    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }

    .nav-toggle {
        display: flex;
    }

    .hero {
        grid-template-columns: 1fr;
        text-align: center;
        padding: 2rem 1rem;
    }

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

    .hero-content p {
        font-size: 1.125rem;
    }

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

    .category-grid {
        grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    }

    .filters {
        flex-direction: column;
    }

    .filter-select {
        width: 100%;
    }

    .video-details {
        flex-direction: column;
        gap: 1rem;
        align-items: flex-start;
    }

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

@media (max-width: 480px) {
    .container {
        padding: 0 0.5rem;
    }

    .hero-actions {
        flex-direction: column;
        width: 100%;
    }

    .btn {
        width: 100%;
        justify-content: center;
    }

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

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

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

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

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

.hidden {
    display: none;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}