/* Reset and Base Styles */
* {
    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: #f5f5f5;
}

/* Header */
header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 3rem 2rem;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    max-width: 1200px;
    margin: 0 auto;
    line-height: 1.3;
}

/* Main Content */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

section {
    background: white;
    margin: 2rem 0;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

section h2 {
    color: #667eea;
    margin-bottom: 1.5rem;
    font-size: 1.8rem;
    border-bottom: 3px solid #667eea;
    padding-bottom: 0.5rem;
}

section h3 {
    color: #555;
    margin-bottom: 0.5rem;
    font-size: 1.3rem;
}

/* Description Section */
.description p {
    margin-bottom: 1rem;
    font-size: 1.1rem;
    color: #555;
    text-align: justify;
}

/* Links Grid */
.link-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.link-card {
    display: block;
    padding: 1.5rem;
    background: linear-gradient(135deg, #667eea15 0%, #764ba215 100%);
    border: 2px solid #667eea;
    border-radius: 8px;
    text-decoration: none;
    color: inherit;
    transition: all 0.3s ease;
    cursor: pointer;
}

.link-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 20px rgba(102, 126, 234, 0.3);
    background: linear-gradient(135deg, #667eea25 0%, #764ba225 100%);
}

.link-card h3 {
    color: #667eea;
    margin-bottom: 0.5rem;
    font-size: 1.3rem;
}

.link-card p {
    color: #666;
    font-size: 0.95rem;
}

/* Video Section */
.video-container {
    margin: 2rem 0;
}

.video-container h3 {
    margin-bottom: 1rem;
    color: #667eea;
}

.video-container iframe,
.video-container video {
    width: 100%;
    max-width: 800px;
    height: 450px;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

.video-container video {
    display: block;
    background: #000;
}

/* Citation Section */
.citation pre {
    background: #f4f4f4;
    border-left: 4px solid #667eea;
    padding: 1.5rem;
    border-radius: 4px;
    overflow-x: auto;
}

.citation code {
    font-family: 'Courier New', Courier, monospace;
    font-size: 0.9rem;
    color: #333;
}

/* Footer */
footer {
    background: #333;
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 3rem;
}

footer p {
    font-size: 0.9rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }

    main {
        padding: 1rem;
    }

    section {
        padding: 1.5rem;
    }

    section h2 {
        font-size: 1.5rem;
    }

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

    .video-container iframe,
    .video-container video {
        height: 250px;
    }
}

@media (max-width: 480px) {
    header {
        padding: 2rem 1rem;
    }

    header h1 {
        font-size: 1.5rem;
    }

    section {
        margin: 1rem 0;
        padding: 1rem;
    }
}