:root {
  --color-primary: #3b82f6;
  --color-primary-dark: #2563eb;
  --color-accent: #0ea5e9;
  --color-bg: #ffffff;
  --color-bg-secondary: #f8fafc;
  --color-bg-tertiary: #f1f5f9;
  --color-text: #1e293b;
  --color-text-secondary: #475569;
  --color-text-muted: #94a3b8;
  --color-border: #e2e8f0;
  --radius: 8px;
  --radius-lg: 12px;
  --max-width: 1100px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  font-size: 15px;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { color: var(--color-primary-dark); text-decoration: underline; }

/* Nav */
.site-nav {
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 3px rgba(0,0,0,.04);
}
.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}
.nav-logo {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
}
.nav-links { display: flex; gap: 20px; }
.nav-links a {
  font-size: 14px;
  color: var(--color-text-secondary);
  text-decoration: none;
  transition: color .2s;
}
.nav-links a:hover { color: var(--color-primary); text-decoration: none; }
.nav-toggle { display: none; background: none; border: none; font-size: 20px; cursor: pointer; }

/* Hero */
.hero {
  text-align: center;
  padding: 60px 24px 40px;
}
.hero h1 {
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--color-text);
}
.hero p {
  font-size: 16px;
  color: var(--color-text-secondary);
  max-width: 600px;
  margin: 0 auto 32px;
}

/* Download section */
.download-section {
  display: flex;
  justify-content: center;
  gap: 24px;
  flex-wrap: wrap;
  margin-bottom: 60px;
}
.download-card {
  text-align: center;
}
.download-card img {
  width: 120px;
  height: auto;
  margin-bottom: 12px;
}
.download-btn {
  display: inline-block;
  padding: 12px 32px;
  background: var(--color-primary);
  color: #fff;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 600;
  text-decoration: none;
  transition: background .2s, transform .1s;
  border: none;
  cursor: pointer;
}
.download-btn:hover {
  background: var(--color-primary-dark);
  color: #fff;
  text-decoration: none;
  transform: translateY(-1px);
}

/* Features */
.features {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px 60px;
}
.features h2 {
  text-align: center;
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 36px;
}
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}
.feature-item {
  text-align: center;
}
.feature-item h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 12px 0 8px;
  color: var(--color-primary);
}
.feature-item p {
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* Articles section */
.articles-section {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px 60px;
}
.articles-section h2 {
  text-align: center;
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 36px;
}
.article-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.article-card {
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
  transition: transform .2s, box-shadow .2s;
  text-decoration: none;
  color: inherit;
  display: block;
}
.article-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(0,0,0,.08);
  text-decoration: none;
}
.article-card-body { padding: 20px; }
.article-tag {
  display: inline-block;
  font-size: 11px;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 4px;
  margin-bottom: 10px;
}
.article-card h3 {
  font-size: 15px;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 8px;
  color: var(--color-text);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.article-card p {
  font-size: 13px;
  color: var(--color-text-muted);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.articles-more {
  text-align: center;
  margin-top: 32px;
}
.articles-more a {
  display: inline-block;
  padding: 12px 36px;
  background: var(--color-primary);
  color: #fff;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 600;
  text-decoration: none;
  transition: background .2s;
}
.articles-more a:hover { background: var(--color-primary-dark); color: #fff; text-decoration: none; }

/* FAQ */
.faq-section {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px 60px;
}
.faq-section h2 {
  text-align: center;
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 36px;
}
.faq-list { max-width: 800px; margin: 0 auto; }
.faq-item {
  border-bottom: 1px solid var(--color-border);
}
.faq-q {
  padding: 16px 0;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--color-text);
}
.faq-a {
  max-height: 0;
  overflow: hidden;
  transition: max-height .3s ease, padding .3s ease;
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.7;
}
.faq-item.open .faq-a {
  max-height: 300px;
  padding-bottom: 16px;
}
.faq-arrow {
  transition: transform .3s;
  font-size: 12px;
  color: var(--color-text-muted);
}
.faq-item.open .faq-arrow { transform: rotate(180deg); }

/* Article detail */
.article-detail {
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 24px 60px;
}
.article-detail h1 {
  font-size: 28px;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--color-text);
  line-height: 1.4;
}
.article-meta {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-bottom: 24px;
  display: flex;
  gap: 16px;
  align-items: center;
}
.article-meta .tag {
  background: var(--color-bg-tertiary);
  padding: 2px 10px;
  border-radius: 4px;
  font-weight: 600;
  color: var(--color-text-secondary);
}
.article-detail h2 {
  font-size: 22px;
  font-weight: 700;
  margin: 32px 0 16px;
  color: var(--color-text);
}
.article-detail h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 24px 0 12px;
  color: var(--color-text);
}
.article-detail p {
  margin-bottom: 16px;
  color: var(--color-text-secondary);
  line-height: 1.8;
}
.article-detail ul, .article-detail ol {
  margin: 0 0 16px 20px;
  color: var(--color-text-secondary);
}
.article-detail li { margin-bottom: 8px; line-height: 1.7; }
.article-detail code {
  background: var(--color-bg-tertiary);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  font-family: "Fira Code", "Consolas", monospace;
}
.article-detail pre {
  background: #1e293b;
  color: #e2e8f0;
  padding: 16px 20px;
  border-radius: var(--radius);
  overflow-x: auto;
  margin: 16px 0;
  font-size: 13px;
  line-height: 1.6;
}
.article-detail pre code { background: none; padding: 0; color: inherit; }
.article-detail blockquote {
  border-left: 4px solid var(--color-primary);
  padding: 8px 20px;
  margin: 16px 0;
  background: var(--color-bg-secondary);
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--color-text-secondary);
}
.article-detail img {
  max-width: 100%;
  border-radius: var(--radius);
  margin: 16px 0;
}
.article-detail a { color: var(--color-primary); }
.breadcrumb {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-bottom: 20px;
}
.breadcrumb a { color: var(--color-text-muted); }
.breadcrumb a:hover { color: var(--color-primary); }

/* Articles listing */
.articles-listing {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 40px 24px 60px;
}
.articles-listing h1 {
  font-size: 28px;
  font-weight: 700;
  margin-bottom: 24px;
}
.category-tabs {
  display: flex;
  gap: 12px;
  margin-bottom: 32px;
  flex-wrap: wrap;
}
.category-tab {
  padding: 6px 16px;
  border-radius: 20px;
  font-size: 14px;
  font-weight: 500;
  background: var(--color-bg-secondary);
  color: var(--color-text-secondary);
  text-decoration: none;
  border: 1px solid var(--color-border);
  transition: all .2s;
}
.category-tab:hover, .category-tab.active {
  background: var(--color-primary);
  color: #fff;
  text-decoration: none;
}

/* Footer */
.site-footer {
  background: var(--color-bg-secondary);
  border-top: 1px solid var(--color-border);
  padding: 40px 24px 20px;
  margin-top: 40px;
}
.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 24px;
  margin-bottom: 24px;
}
.footer-logo { font-size: 18px; font-weight: 700; margin-bottom: 8px; }
.footer-desc { font-size: 13px; color: var(--color-text-secondary); max-width: 400px; }
.footer-links { display: flex; flex-direction: column; gap: 8px; }
.footer-links a { font-size: 13px; color: var(--color-text-secondary); text-decoration: none; }
.footer-links a:hover { color: var(--color-primary); }
.footer-copy {
  max-width: var(--max-width);
  margin: 0 auto;
  padding-top: 20px;
  border-top: 1px solid var(--color-border);
  text-align: center;
}
.footer-copy p { font-size: 12px; color: var(--color-text-muted); }

/* News float */
.news-float {
  display: none;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .nav-links {
    display: none;
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: 16px 24px;
    gap: 12px;
  }
  .nav-links.nav-open { display: flex; }
  .feature-grid { grid-template-columns: 1fr; }
  .article-grid { grid-template-columns: 1fr; }
  .hero h1 { font-size: 24px; }
  .download-section { gap: 16px; }
}