:root {
    --primary-color: #2563eb;
    --secondary-color: #3b82f6;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --background: #ffffff;
    --card-background: #f9fafb;
    --border-color: #e5e7eb;
    --hover-color: #1d4ed8;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* Header */
header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 1.5rem 0;
    box-shadow: var(--shadow);
}

.header-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.5rem;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin: 0;
}

.subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    margin: 0;
}

.header-links {
    display: flex;
    gap: 1.5rem;
    flex-wrap: wrap;
}

.header-links a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
    white-space: nowrap;
}

.header-links a:hover {
    color: var(--hover-color);
}

.header-links i {
    margin-right: 0.25rem;
}

/* Top Navigation */
.top-nav {
    background: var(--primary-color);
    box-shadow: var(--shadow);
    margin-bottom: 3rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-links {
    display: flex;
    gap: 0.5rem;
    overflow-x: auto;
    padding: 0.75rem 0;
    scrollbar-width: thin;
    scrollbar-color: var(--secondary-color) transparent;
}

.nav-links::-webkit-scrollbar {
    height: 4px;
}

.nav-links::-webkit-scrollbar-track {
    background: transparent;
}

.nav-links::-webkit-scrollbar-thumb {
    background: var(--secondary-color);
    border-radius: 2px;
}

.nav-links a {
    color: rgba(255, 255, 255, 0.9);
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 0.375rem;
    font-weight: 500;
    font-size: 0.9rem;
    white-space: nowrap;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-links a:hover {
    background: rgba(255, 255, 255, 0.15);
    color: white;
}

.nav-links a.active {
    background: rgba(255, 255, 255, 0.25);
    color: white;
    font-weight: 600;
}

/* Main Content */
main {
    background: var(--background);
    border-radius: 1rem;
    padding: 3rem 2rem;
    margin-bottom: 3rem;
    box-shadow: var(--shadow-lg);
}

/* Search Section */
.search-section {
    margin-bottom: 3rem;
}

#searchInput {
    width: 100%;
    max-width: 600px;
    padding: 1rem 1.5rem;
    font-size: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 0.5rem;
    transition: all 0.3s ease;
}

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

/* Categories Grid */
.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.category-card {
    background: var(--card-background);
    border: 1px solid var(--border-color);
    border-radius: 0.75rem;
    padding: 1.5rem;
    transition: all 0.3s ease;
    cursor: pointer;
    display: flex;
    flex-direction: column;
}

.category-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.category-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.category-icon i {
    display: block;
}

.category-card h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.count {
    color: var(--primary-color);
    font-weight: 600;
    font-size: 0.875rem;
    margin-bottom: 0.75rem;
}

.category-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.btn {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 0.625rem 1.25rem;
    border-radius: 0.5rem;
    text-decoration: none;
    font-weight: 500;
    text-align: center;
    transition: all 0.3s ease;
    margin-top: auto;
}

.btn:hover {
    background: var(--hover-color);
    transform: scale(1.02);
}

/* Related Indices */
.related-indices {
    border-top: 2px solid var(--border-color);
    padding-top: 2rem;
}

.related-indices h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.index-links {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
}

.index-links a {
    background: var(--card-background);
    color: var(--primary-color);
    padding: 0.75rem 1.25rem;
    border-radius: 0.5rem;
    text-decoration: none;
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
    font-weight: 500;
}

.index-links a:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* Footer */
footer {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 2rem 0;
    text-align: center;
    box-shadow: var(--shadow);
}

footer p {
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
}

footer a:hover {
    color: var(--hover-color);
}

/* Project Cards (for category pages) */
.project-card {
    background: var(--card-background);
    border: 1px solid var(--border-color);
    border-radius: 0.75rem;
    padding: 1.5rem;
    margin-bottom: 1rem;
    transition: all 0.3s ease;
}

.project-card:hover {
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.project-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.project-card h3 a {
    color: var(--text-primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

.project-card h3 a:hover {
    color: var(--primary-color);
}

.project-card .badge {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 0.25rem;
    font-size: 0.75rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.back-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    margin-bottom: 2rem;
    transition: color 0.3s ease;
}

.back-link:hover {
    color: var(--hover-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .header-top {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }

    header h1 {
        font-size: 1.75rem;
    }

    .subtitle {
        font-size: 0.9rem;
    }

    .header-links {
        gap: 1rem;
    }

    .nav-links a {
        font-size: 0.85rem;
        padding: 0.5rem 0.75rem;
    }

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

    main {
        padding: 2rem 1.5rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 1rem;
    }

    header h1 {
        font-size: 1.5rem;
    }

    .category-card {
        padding: 1.25rem;
    }
}