/* Navigation Page Styles */
:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 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);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* Navigation */
.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: var(--transition);
}

.navbar-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.navbar-brand {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 700;
    font-size: 1.25rem;
}

.navbar-brand img {
    width: 32px;
    height: 32px;
    border-radius: 8px;
}

.navbar-nav {
    display: flex;
    align-items: center;
    gap: 8px;
    list-style: none;
}

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 0.9rem;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary-color);
    background: rgba(59, 130, 246, 0.1);
}

.nav-link.active {
    color: var(--primary-color);
    background: rgba(59, 130, 246, 0.1);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 80px 24px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
    opacity: 0.5;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 700;
    color: white;
    margin-bottom: 16px;
    letter-spacing: -0.02em;
}

.hero p {
    font-size: 1.25rem;
    color: rgba(255, 255, 255, 0.9);
    margin-bottom: 32px;
    font-weight: 400;
}

/* Search Box */
.search-container {
    max-width: 600px;
    margin: 0 auto 40px;
    position: relative;
}

.search-box {
    width: 100%;
    padding: 16px 24px 16px 56px;
    font-size: 1rem;
    border: none;
    border-radius: var(--radius-lg);
    background: white;
    box-shadow: var(--shadow-lg);
    transition: var(--transition);
    font-family: inherit;
}

.search-box:focus {
    outline: none;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.search-icon {
    position: absolute;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    font-size: 1.25rem;
}

/* Quick Links */
.quick-links {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

.quick-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-md);
    color: white;
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition);
}

.quick-link:hover {
    background: rgba(255, 255, 255, 0.25);
    transform: translateY(-2px);
}

/* Main Content */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 48px 24px;
}

/* Category Grid */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
    margin-top: 32px;
}

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

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

.category-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 12px;
}

.category-icon {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
}

.category-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
}

.category-count {
    margin-left: auto;
    font-size: 0.75rem;
    color: var(--text-muted);
    background: var(--bg-color);
    padding: 4px 10px;
    border-radius: 20px;
    font-weight: 500;
}

.category-links {
    padding: 16px;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.nav-link-item {
    display: flex;
    align-items: center;
    padding: 12px 16px;
    text-decoration: none;
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    transition: var(--transition);
    font-size: 0.9rem;
    font-weight: 500;
}

.nav-link-item:hover {
    background: var(--bg-color);
    color: var(--primary-color);
}

.nav-link-item::before {
    content: '•';
    margin-right: 8px;
    color: var(--primary-color);
    font-weight: bold;
}

/* Footer */
.footer {
    background: white;
    border-top: 1px solid var(--border-color);
    padding: 48px 24px 24px;
    margin-top: 64px;
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    text-align: center;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-bottom: 24px;
}

.social-link {
    width: 44px;
    height: 44px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-color);
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
    font-size: 1.125rem;
}

.social-link:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.footer-text {
    color: var(--text-muted);
    font-size: 0.875rem;
}

.footer-text a {
    color: var(--primary-color);
    text-decoration: none;
}

/* Loading State */
.loading-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 300px;
}

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* No Results */
.no-results {
    text-align: center;
    padding: 64px 24px;
    color: var(--text-muted);
}

.no-results i {
    font-size: 3rem;
    margin-bottom: 16px;
    display: block;
}

/* Responsive */
@media (max-width: 768px) {
    .navbar-nav {
        display: none;
    }

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

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

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

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

/* Category Icon Colors */
.icon-main { background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; }
.icon-common { background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%); color: white; }
.icon-ai { background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%); color: white; }
.icon-python { background: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%); color: white; }
.icon-learning { background: linear-gradient(135deg, #fa709a 0%, #fee140 100%); color: white; }
.icon-writing { background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%); color: #333; }
.icon-tools { background: linear-gradient(135deg, #d299c2 0%, #fef9d7 100%); color: #333; }