:root {
  --primary-color: #0066cc;
  --primary-hover: #005bb5;
  --text-main: #333333;
  --text-muted: #666666;
  --bg-body: #f8f9fa;
  --bg-card: #ffffff;
  --border-color: #e5e7eb;
  --border-radius: 8px;
  --container-width: 1200px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 32px;
  --spacing-xl: 64px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Arial, sans-serif; color: var(--text-main); background-color: var(--bg-body); line-height: 1.6; font-size: 16px; }
a { color: var(--primary-color); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--primary-hover); text-decoration: underline; }
ul { list-style: none; }
img { max-width: 100%; height: auto; display: block; border-radius: var(--border-radius); }

.container { max-width: var(--container-width); margin: 0 auto; padding: 0 var(--spacing-md); }
.section { padding: var(--spacing-xl) 0; }
.section-title { text-align: center; font-size: 2rem; margin-bottom: var(--spacing-lg); color: #111; }

.grid { display: grid; gap: var(--spacing-lg); }
.grid-2 { grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); }
.grid-4 { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }

.site-header { background-color: var(--bg-card); box-shadow: 0 2px 4px rgba(0,0,0,0.05); position: sticky; top: 0; z-index: 100; }
.nav-container { display: flex; justify-content: space-between; align-items: center; height: 70px; }
.logo a { font-size: 1.5rem; font-weight: bold; color: var(--primary-color); text-decoration: none; }
.main-nav ul { display: flex; gap: var(--spacing-lg); }
.main-nav a { color: var(--text-main); font-weight: 500; }
.main-nav a:hover { color: var(--primary-color); text-decoration: none; }

.hero { background-color: var(--bg-card); padding: 80px 0; text-align: center; border-bottom: 1px solid var(--border-color); }
.hero h1 { font-size: 2.5rem; margin-bottom: var(--spacing-md); color: #111; }
.hero p { font-size: 1.2rem; color: var(--text-muted); max-width: 800px; margin: 0 auto var(--spacing-lg); }

.btn { display: inline-block; padding: 12px 24px; border-radius: var(--border-radius); font-weight: bold; text-align: center; cursor: pointer; text-decoration: none; }
.btn:hover { text-decoration: none; }
.btn-primary { background-color: var(--primary-color); color: #fff; }
.btn-primary:hover { background-color: var(--primary-hover); color: #fff; }

.card { background-color: var(--bg-card); border: 1px solid var(--border-color); border-radius: var(--border-radius); padding: var(--spacing-lg); transition: transform 0.2s, box-shadow 0.2s; }
.card:hover { transform: translateY(-5px); box-shadow: 0 4px 12px rgba(0,0,0,0.1); }
.card h2, .card h3 { margin-bottom: var(--spacing-md); color: #111; }

.link-list { padding-left: var(--spacing-md); list-style: disc; margin-bottom: var(--spacing-md); }
.link-list li { margin-bottom: var(--spacing-sm); }

.faq-item { background-color: var(--bg-card); border: 1px solid var(--border-color); border-radius: var(--border-radius); margin-bottom: var(--spacing-md); overflow: hidden; }
.faq-item summary { padding: var(--spacing-md); font-weight: bold; cursor: pointer; display: flex; justify-content: space-between; }
.faq-item summary::after { content: "+"; color: var(--primary-color); }
.faq-item[open] summary::after { content: "-"; }
.faq-content { padding: 0 var(--spacing-md) var(--spacing-md); color: var(--text-muted); }

.breadcrumb { padding: var(--spacing-md) 0; font-size: 0.9rem; color: var(--text-muted); }
.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--primary-color); }
.breadcrumb .separator { margin: 0 var(--spacing-sm); }

.site-footer { background-color: #222; color: #ccc; padding: var(--spacing-xl) 0 var(--spacing-md); margin-top: 40px; }
.footer-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: var(--spacing-lg); margin-bottom: var(--spacing-lg); }
.footer-widget h4 { color: #fff; margin-bottom: var(--spacing-md); font-size: 1.1rem; }
.footer-widget a { color: #aaa; }
.footer-widget a:hover { color: #fff; }
.footer-bottom { text-align: center; padding-top: var(--spacing-md); border-top: 1px solid #444; font-size: 0.9rem; }

.article-grid { display: grid; grid-template-columns: 3fr 1fr; gap: 40px; }
.article-body { padding: 40px; background-color: var(--bg-card); border-radius: var(--border-radius); box-shadow: 0 2px 10px rgba(0,0,0,0.05); }
.article-body h1 { font-size: 2.2rem; margin-bottom: 15px; color: #111; }
.article-body h2 { font-size: 1.8rem; margin: 32px 0 16px; color: #111; border-bottom: 2px solid var(--border-color); padding-bottom: 8px;}
.article-body h3 { font-size: 1.4rem; margin: 24px 0 12px; color: #222; }
.article-body p { margin-bottom: 16px; font-size: 1.05rem; }
.article-body ul, .article-body ol { margin-bottom: 24px; padding-left: 24px; }
.article-body li { margin-bottom: 8px; font-size: 1.05rem; }
.article-meta { color: #888; font-size: 0.9rem; margin-bottom: 32px; padding-bottom: 16px; border-bottom: 1px solid var(--border-color); }
.article-sidebar { position: sticky; top: 90px; }
.cta-box { background-color: #f0f7ff; border: 1px solid #cce0ff; text-align: center; padding: 24px; border-radius: var(--border-radius); margin-bottom: 24px; }

.related-posts { margin-top: 40px; padding-top: 20px; border-top: 2px solid var(--border-color); }
.related-posts h3 { margin-bottom: 15px; font-size: 1.3rem; }
.related-posts ul { list-style: none; padding-left: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 15px; }
.related-posts li { background: var(--bg-body); padding: 15px; border-radius: var(--border-radius); border: 1px solid var(--border-color); }
.related-posts li a { display: block; font-weight: 500; color: #333; }
.related-posts li a:hover { color: var(--primary-color); }

.text-center { text-align: center; }
.mt-2 { margin-top: var(--spacing-md); }
.mb-2 { margin-bottom: var(--spacing-md); }
.pt-0 { padding-top: 0; }

@media (max-width: 992px) {
  .article-grid { grid-template-columns: 1fr; }
}
@media (max-width: 768px) {
  .nav-container { flex-direction: column; height: auto; padding: var(--spacing-md) 0; }
  .main-nav ul { margin-top: var(--spacing-md); flex-wrap: wrap; justify-content: center; gap: var(--spacing-md); }
  .hero h1 { font-size: 2rem; }
}