:root {
  --primary: #1a56db;
  --primary-dark: #1e40af;
  --accent: #059669;
  --text: #1f2937;
  --text-light: #6b7280;
  --bg: #ffffff;
  --bg-alt: #f9fafb;
  --border: #e5e7eb;
  --radius: 8px;
  --max-width: 1200px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  font-size: 17px;
}

.container { max-width: var(--max-width); margin: 0 auto; padding: 0 1.5rem; }

/* Header */
.site-header {
  border-bottom: 1px solid var(--border);
  padding: 1rem 0;
  position: sticky;
  top: 0;
  background: var(--bg);
  z-index: 100;
}
.site-header .container { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 1rem; }
.logo { text-decoration: none; color: var(--primary); font-size: 1.25rem; }
.logo-img { height: 40px; width: auto; display: block; }
.logo .tagline { display: block; font-size: 0.75rem; color: var(--text-light); font-weight: normal; }
.main-nav { display: flex; gap: 1.5rem; flex-wrap: wrap; }
.main-nav a { text-decoration: none; color: var(--text); font-size: 0.9rem; font-weight: 500; }
.main-nav a:hover, .main-nav a.active { color: var(--primary); }

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
  color: white;
  padding: 4rem 1.5rem;
  text-align: center;
}
.hero h1 { font-size: 2.5rem; margin-bottom: 1rem; }
.hero-subtitle { font-size: 1.2rem; opacity: 0.9; max-width: 600px; margin: 0 auto; }

/* Article Grid */
.article-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1.5rem;
  margin: 2rem 0;
}
.card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: box-shadow 0.2s;
}
.card:hover { box-shadow: 0 4px 12px rgba(0,0,0,0.08); }
.card h2, .card h3 { margin-bottom: 0.5rem; }
.card h2 a, .card h3 a { text-decoration: none; color: var(--text); }
.card h2 a:hover, .card h3 a:hover { color: var(--primary); }
.card-category { font-size: 0.8rem; color: var(--accent); font-weight: 600; text-transform: uppercase; letter-spacing: 0.05em; }
.card p { color: var(--text-light); font-size: 0.95rem; margin: 0.5rem 0; }
.read-more { color: var(--primary); text-decoration: none; font-weight: 500; font-size: 0.9rem; }

/* Article */
.article { padding: 2rem 0; }
.article-header { margin-bottom: 2rem; }
.article-header h1 { font-size: 2.2rem; line-height: 1.3; }
.article-meta { color: var(--text-light); font-size: 0.9rem; margin-top: 0.5rem; }
.article-meta a { color: var(--primary); text-decoration: none; }
.article-content { max-width: 780px; }
.article-content h2 { font-size: 1.6rem; margin: 2rem 0 1rem; color: var(--text); border-bottom: 2px solid var(--primary); padding-bottom: 0.3rem; }
.article-content h3 { font-size: 1.3rem; margin: 1.5rem 0 0.75rem; }
.article-content p { margin-bottom: 1.2rem; }
.article-content ul, .article-content ol { margin: 1rem 0 1.2rem 1.5rem; }
.article-content li { margin-bottom: 0.5rem; }
.article-content table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; }
.article-content th, .article-content td { border: 1px solid var(--border); padding: 0.75rem; text-align: left; }
.article-content th { background: var(--bg-alt); font-weight: 600; }
.article-content blockquote { border-left: 4px solid var(--primary); padding: 1rem 1.5rem; background: var(--bg-alt); margin: 1.5rem 0; border-radius: 0 var(--radius) var(--radius) 0; }

/* CTA boxes */
.cta-box {
  background: linear-gradient(135deg, #eff6ff 0%, #f0fdf4 100%);
  border: 1px solid var(--primary);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin: 2rem 0;
  text-align: center;
}
.cta-box a { display: inline-block; background: var(--primary); color: white; padding: 0.75rem 2rem; border-radius: var(--radius); text-decoration: none; font-weight: 600; margin-top: 0.75rem; }

/* TOC */
.toc { background: var(--bg-alt); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.5rem; margin-bottom: 2rem; max-width: 780px; }
.toc h2 { font-size: 1.1rem; margin-bottom: 0.75rem; }
.toc > nav > ul { list-style: none; margin: 0; padding: 0; }
.toc ul ul { list-style: none; margin: 0; padding-left: 1.25rem; }
.toc li { margin: 0.3rem 0; }
.toc a { text-decoration: none; color: var(--primary); font-size: 0.9rem; }

/* Tags */
.article-tags { margin: 2rem 0; display: flex; gap: 0.5rem; flex-wrap: wrap; }
.tag { background: var(--bg-alt); border: 1px solid var(--border); padding: 0.25rem 0.75rem; border-radius: 20px; text-decoration: none; color: var(--text-light); font-size: 0.85rem; }

/* CTA Section */
.cta-section { text-align: center; padding: 3rem 0; }
.cta-grid { display: flex; justify-content: center; gap: 1rem; flex-wrap: wrap; margin-top: 1.5rem; }
.cta-card { background: var(--primary); color: white; padding: 1rem 2rem; border-radius: var(--radius); text-decoration: none; font-weight: 600; }
.cta-card:hover { background: var(--primary-dark); }

/* Related */
.related-posts { border-top: 1px solid var(--border); padding-top: 2rem; margin-top: 2rem; }

/* Footer */
.site-footer { background: var(--text); color: #d1d5db; padding: 3rem 0 1.5rem; margin-top: 4rem; }
.site-footer h3 { color: white; margin-bottom: 0.75rem; font-size: 1rem; }
.site-footer ul { list-style: none; }
.site-footer a { color: #9ca3af; text-decoration: none; }
.site-footer a:hover { color: white; }
.footer-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 2rem; }
.copyright { text-align: center; margin-top: 2rem; padding-top: 1.5rem; border-top: 1px solid #374151; font-size: 0.85rem; }

/* Responsive */
@media (max-width: 768px) {
  .hero h1 { font-size: 1.8rem; }
  .article-header h1 { font-size: 1.6rem; }
  .article-grid { grid-template-columns: 1fr; }
}