:root{
  --bg:#f5f3f1; /* warm gray background */
  --paper:#ffffff;
  --charcoal:#222428; /* 炭黑 */
  --muted:#8a857f;
  --accent:#2d2d2d;
  --border:rgba(34,36,40,0.08);
  --radius:2px; /* 2px 小圆角 */
  --container-min:1120px;
  --container-max:1320px;
  --gap:28px;
  --side-width:320px;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans CJK SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color-scheme: light;
}

/* Reset-ish */
*{box-sizing:border-box}
html,body{height:100%;}
body{margin:0;background:var(--bg);color:var(--charcoal);line-height:1.6;font-size:16px;-webkit-font-smoothing:antialiased;}
.page-bg{min-height:100vh;display:flex;flex-direction:column;}

a{color:inherit;text-decoration:none}

/* Header: 双层报头但第二层极窄 */
.site-header{padding:18px 20px 0 20px}
.header-row{display:flex;align-items:center;justify-content:space-between}
.header-row-main{gap:12px}
.site-title{font-weight:700;color:var(--charcoal);font-size:20px}
.header-right{font-size:13px;color:var(--muted)}
.header-row-slim{height:6px;margin-top:8px;background:transparent}

/* viewport / sheet grid */
.viewport{flex:1;padding:28px 18px 40px}
.sheet-grid{display:block;max-width:1200px;margin:24px auto;}

/* Article and side are arranged differently per breakpoint */
.article{background:var(--paper);border:1px solid var(--border);border-radius:var(--radius);padding:28px;box-shadow:none}
.article-title{font-size:36px;line-height:1.06;margin:0 0 10px 0;font-weight:800;letter-spacing:-0.01em;}
.article-meta{font-size:13px;color:var(--muted);display:flex;gap:12px;margin-bottom:12px}
.article-summary{font-size:15px;color:var(--charcoal);margin:0 0 16px}
.article-body{font-size:16px;color:var(--charcoal)}
.article-body p{margin:0 0 12px}

/* FAQ 横线问答列表风格 */
.faq-section{margin-top:22px}
.section-title{font-size:18px;margin:0 0 10px;color:var(--charcoal)}
.faq-list > *{padding:12px 0;border-top:1px solid var(--border)}
.faq-list > *:first-child{border-top:0;padding-top:0}

/* Side panel */
.side{margin-top:18px}
.side-panel{background:transparent;border:1px solid var(--border);border-radius:var(--radius);padding:12px;margin-bottom:12px}
.side-heading{font-size:13px;color:var(--muted);margin:0 0 8px}
.keywords{font-size:14px;color:var(--charcoal)}

/* Related visual signature: 反向色块标题栏 + 编号列表 */
.related-panel{overflow:hidden}
.related-header{background:var(--charcoal);color:#fff;padding:10px 12px;font-weight:700}
.related-body{padding:10px}
.related-body ol{margin:0;padding-left:20px}
.related-body li{margin:6px 0}

/* Ad slots — independent containers, non-intrusive */
.ad-slot{margin:8px 0;padding:6px;border-radius:var(--radius);border:1px dashed var(--border);background:transparent;font-size:13px;color:var(--muted)}
.ad-top{margin-bottom:12px}
.ad-middle{margin-top:18px;margin-bottom:18px}
.ad-bottom{margin-top:18px}

/* Footer */
.site-footer{padding:18px 20px;background:transparent;border-top:1px solid rgba(34,36,40,0.03);text-align:center;color:var(--muted);font-size:13px}

/* --- Desktop: 1024px 及以上 --- */
@media (min-width:1024px){
  .viewport{padding:48px 20px}
  .sheet-grid{display:grid;grid-template-columns:1fr var(--side-width);column-gap:28px;max-width:var(--container-max);min-width:var(--container-min);}

  /* Offset-sheet: article appears as a slightly left-offset paper without shadow or large radius */
  .article{transform:translateX(-36px);border-radius:var(--radius);padding:36px}

  /* 标题向左越出正文基线 */
  .article-title{font-size:44px;margin-left:-24px;max-height:calc(2 * 1.06em);overflow:hidden}

  /* 右侧保留窄边注 */
  .side{position:relative;top:36px}

  /* 更紧凑的密度 */
  .article-body{font-size:17px}
}

/* --- Mobile: 767px 及以下 --- */
@media (max-width:767px){
  :root{--gap:16px}
  body{font-size:15px}
  .viewport{padding:14px}
  .sheet-grid{display:block;max-width:100%;margin:0 auto}

  /* 取消偏移和越界，安全边距内 */
  .article{transform:none;border-radius:var(--radius);padding:16px}
  .article-title{font-size:20px;margin-left:0;line-height:1.12}
  .article-meta{flex-direction:column;gap:6px}
  .article-summary{font-size:15px}

  /* 侧栏下移，变为区块式自然堆叠 */
  .side{margin-top:18px}
  .side-panel{padding:12px}
  .related-header{padding:8px}

  /* 防止横向滚动 */
  html,body{overflow-x:hidden}
  .article-body img, .article-body table{max-width:100%;height:auto}
}

/* Accessibility / readable contrasts */
.article-title, .site-title{color:var(--accent)}

/* Avoid shadows (forbidden) */
/* Explicitly do not use box-shadow for information hierarchy */