/* Variables and base (system fonts) */
:root{
  --bg:#ffffff;
  --paper:#f7f6f4; /* warm grey accent */
  --ink:#222222; /* charcoal */
  --muted:#6c6c68;
  --accent:#444444;
  --line: #e6e4e2; /* fine separator */
  --max-content-width: clamp(1120px, 75vw, 1200px);
  --gap:12px; /* compact density */
  --nav-hit:44px; /* minimum touch target */
}

*{box-sizing:border-box}
html,body{height:100%;margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", "Microsoft YaHei", sans-serif;line-height:1.45;font-size:15px}

/* Header: 左右分置的编辑部报头，居中站名加左右文本链接 */
.site-header{border-bottom:1px solid var(--line);background:linear-gradient(transparent, transparent);padding:10px 0}
.header-inner{max-width:var(--max-content-width);margin:0 auto;display:flex;align-items:center;justify-content:space-between;gap:8px;padding:6px 18px}
.nav-left,.nav-right{display:flex;gap:10px;align-items:center;color:var(--muted);font-size:13px}
.nav-item{padding:6px 8px;line-height:1}
.brand{flex:0 0 auto;text-align:center}
.home-link{color:var(--ink);text-decoration:none;font-weight:600;font-size:18px;display:inline-block;padding:6px 10px}
.home-link:focus{outline:1px solid var(--line)}

/* Layout wrapper */
.wrap{max-width:var(--max-content-width);margin:18px auto;padding:0 18px}
.layout-grid{display:grid;grid-template-columns:1fr;gap:18px}

/* Primary article */
.primary{min-width:0}
.article{background:transparent;border:0}
.article-header{display:block;border-bottom:1px solid var(--line);padding-bottom:10px;margin-bottom:12px}
.title-area{display:block}
.article-title{font-size:22px;color:var(--ink);margin:0 0 6px 0;font-weight:700}
.meta{color:var(--muted);font-size:13px}
.summary-area{margin-top:8px}
.summary{color:var(--accent);margin:0;font-size:14px}

/* Article body */
.article-body{padding:0;margin:0}
.content{color:var(--ink);font-size:15px;word-wrap:break-word}
.content p{margin:0 0 12px}

/* FAQ section - desktop will render as left question / right answer table-like */
.faq-section{margin-top:18px;border-top:1px solid var(--line);padding-top:12px}
.section-title{font-size:16px;margin:0 0 10px 0;color:var(--ink);font-weight:600}
.faq dl{margin:0}
.faq dt{font-weight:600;padding:8px 0;color:var(--accent)}
.faq dd{margin:0 0 12px 0;padding:8px 0;color:var(--muted)}

/* Related pattern: two-column摘要列表 on desktop, dense */
.related-section{margin-top:18px;border-top:1px solid var(--line);padding-top:12px}
.related{display:block}
.related a{color:var(--ink);text-decoration:none}

/* Sidebar */
.sidebar{border-left:1px solid var(--line);padding-left:18px}
.side-block{padding:6px 0;border-bottom:1px dashed var(--line);margin-bottom:6px}
.side-title{font-size:13px;margin:0 0 8px 0;color:var(--accent)}
.side-note{margin:0;color:var(--muted);font-size:13px}
.side-list{list-style:none;padding:0;margin:0}
.side-list li{padding:6px 0}
.side-link{color:var(--muted)}

/* Ads are independent blocks, not floating */
.ad{max-width:var(--max-content-width);margin:12px auto;padding:10px;border:1px dashed var(--line);color:var(--muted);font-size:13px}
.ad-top{margin-top:12px}

/* Footer */
.site-footer{border-top:1px solid var(--line);padding:12px 0;margin-top:18px}
.footer-inner{max-width:var(--max-content-width);margin:0 auto;padding:0 18px;color:var(--muted);font-size:13px}

/* Accessibility: ensure nav items are large enough for touch */
.nav-item, .home-link, .side-link{min-height:var(--nav-hit);display:inline-flex;align-items:center}

/* Forbidden: no shadows, no large radii, keep edges crisp */

/* Mobile-specific rules (explicit) */
@media (max-width: 767px){
  :root{--gap:10px}
  .header-inner{padding:6px 12px}
  .nav-left,.nav-right{font-size:13px;gap:8px;overflow:auto}
  .nav-left,.nav-right{white-space:nowrap}
  .wrap{padding:0 12px}
  .layout-grid{grid-template-columns:1fr;gap:12px}
  .article-title{font-size:18px}
  .summary{font-size:14px}
  /* Title composition stacks naturally on mobile */
  .article-header{display:block}
  .summary-area{margin-top:8px}
  /* Sidebar moves below content: achieved by single column layout */
  .sidebar{border-left:0;padding-left:0;border-top:1px solid var(--line);padding-top:12px}
  .ad{margin-left:12px;margin-right:12px}
  /* Related becomes single column list */
  .related{display:block}
  .faq dl{display:block}
  /* Ensure no horizontal scrolling at 320px */
  body{font-size:15px}
}

/* Desktop-specific rules (explicit) */
@media (min-width: 1024px){
  .wrap{padding:0}
  .layout-grid{grid-template-columns:1fr 360px;gap:24px;align-items:start}
  .title-area{grid-column:1}
  .article-header{display:grid;grid-template-columns:1fr 320px;gap:20px;align-items:start}
  /* Title 与 摘要 左右分置 */
  .article-title{font-size:26px}
  .summary{font-size:15px;color:var(--muted)}
  /* Content wide, sidebar narrow */
  .primary{min-width:0}
  .sidebar{padding-left:24px}
  /* FAQ: left question, right answer in table-like grid */
  .faq dl{display:grid;grid-template-columns:260px 1fr;gap:8px 20px;border-top:0}
  .faq dt{padding:10px 0;border-bottom:1px solid var(--line)}
  .faq dd{padding:10px 0;border-bottom:1px solid var(--line);margin:0}
  /* Related: two-column摘要列表 */
  .related{display:grid;grid-template-columns:1fr 1fr;gap:10px}
  .related a{display:block;padding:6px 0;border-bottom:1px solid var(--line);font-size:14px}
}

/* Ensure content images or wide elements do not overflow */
.content img, .content table{max-width:100%;height:auto}

/* Small utility */
.sep{color:var(--muted);margin:0 6px}
.now{color:var(--muted)}