:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --text-color: #333333;
    --light-text: #666666;
    --bg-color: #f8f9fa;
    --white: #ffffff;
    --border-color: #e5e7eb;
    --container-width: 1200px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

a {
    color: inherit;
    text-decoration: none;
    transition: color 0.3s;
}

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

img {
    max-width: 100%;
    height: auto;
    display: block;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.site-header {
    background: var(--white);
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-wrapper {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo {
    font-size: 24px;
    font-weight: bold;
    color: var(--primary-color);
}

.main-nav ul {
    display: flex;
    list-style: none;
    gap: 20px;
}

.main-nav a {
    font-weight: 500;
    padding: 8px 0;
}

.main-nav a:hover {
    color: var(--primary-color);
    border-bottom: 2px solid var(--primary-color);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: var(--white);
    padding: 60px 0;
    text-align: center;
    margin-bottom: 40px;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 20px;
}

.hero p {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* Grid Layout */
.grid-cols-3 {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
}

.grid-cols-4 {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 20px;
}

/* Card */
.card {
    background: var(--white);
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    transition: transform 0.3s;
}

.card:hover {
    transform: translateY(-5px);
}

.card-img {
    height: 200px;
    overflow: hidden;
}

.card-img img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.card-body {
    padding: 20px;
}

.card-title {
    font-size: 1.1rem;
    margin-bottom: 10px;
    line-height: 1.4;
}

.card-meta {
    font-size: 0.9rem;
    color: var(--light-text);
    display: flex;
    justify-content: space-between;
    margin-top: 15px;
}

/* Footer */
.site-footer {
    background: #1f2937;
    color: #9ca3af;
    padding: 60px 0 20px;
    margin-top: 60px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 40px;
    margin-bottom: 40px;
}

.footer-section h3 {
    color: var(--white);
    margin-bottom: 20px;
}

.footer-links li {
    list-style: none;
    margin-bottom: 10px;
}

.copyright {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid #374151;
}

/* Article Detail */
.article-header {
    margin-bottom: 30px;
    text-align: center;
}

.article-title {
    font-size: 2.5rem;
    margin-bottom: 15px;
}

.article-meta {
    color: var(--light-text);
}

.article-content {
    background: var(--white);
    padding: 40px;
    border-radius: 8px;
    box-shadow: 0 2px 15px rgba(0,0,0,0.05);
    font-size: 1.1rem;
    line-height: 1.8;
}

.article-content h2 { margin: 30px 0 15px; }
.article-content p { margin-bottom: 20px; }
.article-content img { margin: 20px auto; border-radius: 4px; }

/* Responsive */
@media (max-width: 768px) {
    .nav-wrapper {
        flex-direction: column;
        height: auto;
        padding: 15px 0;
    }
    
    .main-nav ul {
        margin-top: 15px;
        flex-wrap: wrap;
        justify-content: center;
    }

    .hero h1 { font-size: 2rem; }
    
    .article-title { font-size: 1.8rem; }
    .article-content { padding: 20px; }
}