:root {
  --color-primary: #1a5f7a;
  --color-secondary: #2d8fa3;
  --color-bg: #fafafa;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-muted: #6b7280;
  --color-border: #e5e7eb;
  --font-sans: system-ui, -apple-system, sans-serif;
  --max-width: 900px;
  --spacing: 1.5rem;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: var(--font-sans); background: var(--color-bg); color: var(--color-text); line-height: 1.6; }
.container { max-width: var(--max-width); margin: 0 auto; padding: var(--spacing); }

.site-header { background: var(--color-surface); border-bottom: 1px solid var(--color-border); position: sticky; top: 0; z-index: 100; }
.main-nav { display: flex; justify-content: space-between; align-items: center; max-width: var(--max-width); margin: 0 auto; padding: 1rem var(--spacing); }
.logo { font-weight: 700; color: var(--color-primary); text-decoration: none; font-size: 1.25rem; }
.nav-links { display: flex; gap: 2rem; list-style: none; }
.nav-links a { color: var(--color-text); text-decoration: none; font-weight: 500; transition: color 0.2s; }
.nav-links a:hover { color: var(--color-primary); }

.site-main { min-height: calc(100vh - 200px); }
.site-footer { background: var(--color-surface); border-top: 1px solid var(--color-border); padding: 2rem var(--spacing); text-align: center; color: var(--color-text-muted); font-size: 0.875rem; }

/* Hero */
.hero { text-align: center; padding: 4rem 1rem; background: linear-gradient(135deg, var(--color-primary), var(--color-secondary)); color: white; margin: 0 calc(-1 * var(--spacing)) 3rem; }
.hero h1 { font-size: 3rem; margin-bottom: 1rem; }
.hero .tagline { font-size: 1.25rem; opacity: 0.9; max-width: 600px; margin: 0 auto; }

/* Sections */
.featured, .latest-articles { margin-bottom: 4rem; }
.featured h2, .latest-articles h2 { font-size: 1.75rem; margin-bottom: 1.5rem; color: var(--color-text); }

/* Grids */
.project-grid, .article-grid, .doc-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.5rem; margin-top: 1.5rem; }

/* Cards */
.project-card, .article-card, .doc-card { background: var(--color-surface); border: 1px solid var(--color-border); border-radius: 8px; overflow: hidden; transition: transform 0.2s, box-shadow 0.2s; }
.project-card:hover, .article-card:hover, .doc-card:hover { transform: translateY(-4px); box-shadow: 0 12px 24px rgba(0,0,0,0.1); }
.project-card img, .article-card img { width: 100%; height: 160px; object-fit: cover; }
.project-card-content, .article-card-content, .doc-card-content { padding: 1.25rem; }
.project-card h3, .article-card h3, .doc-card h3 { font-size: 1.125rem; margin-bottom: 0.5rem; }
.project-card h3 a, .article-card h3 a, .doc-card h3 a { color: var(--color-text); text-decoration: none; }
.project-card h3 a:hover, .article-card h3 a:hover, .doc-card h3 a:hover { color: var(--color-primary); }
.project-card p, .article-card p, .doc-card p { color: var(--color-text-muted); font-size: 0.875rem; margin-bottom: 1rem; }
.btn { display: inline-block; padding: 0.5rem 1rem; background: var(--color-primary); color: white; text-decoration: none; border-radius: 4px; font-size: 0.875rem; font-weight: 500; transition: background 0.2s; }
.btn:hover { background: var(--color-secondary); }

/* Page Content */
.page-header { margin-bottom: 2rem; padding-bottom: 1rem; border-bottom: 1px solid var(--color-border); }
.page-title { font-size: 2rem; font-weight: 700; margin-bottom: 0.5rem; }
.page-meta { color: var(--color-text-muted); font-size: 0.875rem; }
.page-content { font-size: 1rem; }
.page-content h2 { font-size: 1.5rem; margin: 2rem 0 1rem; padding-bottom: 0.5rem; border-bottom: 1px solid var(--color-border); }
.page-content h3 { font-size: 1.25rem; margin: 1.5rem 0 0.75rem; }
.page-content p { margin-bottom: 1rem; }
.page-content ul, .page-content ol { margin: 1rem 0 1rem 1.5rem; }
.page-content code { background: #f1f5f9; padding: 0.125rem 0.375rem; border-radius: 3px; font-size: 0.875em; }
.page-content pre { background: #1e293b; color: #e2e8f0; padding: 1rem; border-radius: 6px; overflow-x: auto; margin: 1rem 0; }
.page-content pre code { background: none; padding: 0; color: inherit; }
.page-content img { max-width: 100%; height: auto; border-radius: 6px; margin: 1.5rem 0; }
.page-content blockquote { border-left: 4px solid var(--color-primary); padding-left: 1rem; color: var(--color-text-muted); margin: 1.5rem 0; font-style: italic; }
.page-content table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; }
.page-content th, .page-content td { border: 1px solid var(--color-border); padding: 0.75rem; text-align: left; }
.page-content th { background: var(--color-bg); font-weight: 600; }

/* Responsive */
@media (max-width: 640px) {
  .nav-links { display: none; }
  .hero h1 { font-size: 2rem; }
  .page-title { font-size: 1.5rem; }
  .project-grid, .article-grid, .doc-grid { grid-template-columns: 1fr; }
}