:root{
  --ink:#16202f; --muted:#5b6b85; --line:#e2e8f2; --blue:#2f6bff;
  --soft:#f6f9ff; --max:920px;
}
*{box-sizing:border-box}
body{margin:0;background:#fff;color:var(--ink);
  font:15px/1.75 -apple-system,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",
  "Noto Sans CJK SC","Source Han Sans SC",system-ui,"Segoe UI",Roboto,sans-serif;
  -webkit-font-smoothing:antialiased}
a{color:var(--blue);text-decoration:none}
a:hover{text-decoration:underline}
.wrap{max-width:var(--max);margin:0 auto;padding:0 22px}
header{border-bottom:1px solid var(--line);background:rgba(255,255,255,.94);
  position:sticky;top:0;z-index:5;backdrop-filter:saturate(160%) blur(9px)}
header .in{display:flex;align-items:center;justify-content:space-between;height:60px;gap:16px}
.brand{font-weight:800;letter-spacing:.02em;color:var(--ink)}
.brand i{display:inline-block;width:10px;height:10px;border-radius:50%;
  background:var(--blue);margin-right:8px;vertical-align:1px}
nav a{color:var(--muted);font-size:13.5px;margin-left:16px;white-space:nowrap}
nav a.on{color:var(--ink);font-weight:700}
main{padding:44px 0 72px}
.eyebrow{color:var(--blue);font-size:12.5px;font-weight:800;letter-spacing:.08em}
h1{font-size:clamp(26px,4vw,36px);margin:8px 0 10px;letter-spacing:-.02em}
.lead{color:var(--muted);margin:0 0 14px}
.meta{display:flex;flex-wrap:wrap;gap:8px 18px;color:var(--muted);font-size:12.5px;
  border-top:1px solid var(--line);border-bottom:1px solid var(--line);
  padding:12px 0;margin:18px 0 26px}
.meta b{color:var(--ink)}
.toc{background:var(--soft);border:1px solid var(--line);border-radius:14px;
  padding:16px 20px;margin:0 0 26px}
.toc>b{display:block;margin-bottom:6px}
.toc ol{margin:0;padding-left:20px;columns:2;column-gap:28px;font-size:13.5px}
.toc a{color:#2453cc}
h2{font-size:19px;margin:34px 0 10px;letter-spacing:-.01em;scroll-margin-top:74px}
h2 .no{display:inline-flex;width:24px;height:24px;border-radius:50%;
  background:var(--blue);color:#fff;font-size:12px;align-items:center;
  justify-content:center;margin-right:8px;vertical-align:2px}
h3{font-size:15.5px;margin:20px 0 6px}
p,li{color:#2b3a52}
ul,ol{padding-left:22px}
li{margin:4px 0}
code{background:#f1f5fb;border-radius:5px;padding:1px 5px;font-size:13px;
  overflow-wrap:anywhere;word-break:break-word}
table{width:100%;border-collapse:collapse;margin:12px 0;font-size:14px}
th,td{border:1px solid var(--line);text-align:left;padding:8px 10px;vertical-align:top}
th{background:var(--soft);font-weight:700}
.callout{border-radius:12px;padding:13px 16px;margin:16px 0;font-size:14px}
.callout.info{background:#eef4ff;border:1px solid #d6e2ff}
.callout.warn{background:#fff7e8;border:1px solid #f3dfb5}
.callout.rule{background:#fff2f2;border:1px solid #f3cccc}
.callout>b{display:block;margin-bottom:4px}
.small{color:var(--muted);font-size:13px}
footer{border-top:1px solid var(--line);background:var(--soft);
  padding:26px 0;color:var(--muted);font-size:12.5px}
footer .cols{display:flex;flex-wrap:wrap;gap:18px 40px;justify-content:space-between}
footer b{color:var(--ink)}
footer a{color:var(--muted)}
footer a:hover{color:var(--blue)}
@media(max-width:640px){
  .toc ol{columns:1}
  nav a{margin-left:10px;font-size:12.5px}
  header .in{height:auto;min-height:54px;flex-wrap:wrap;padding:8px 0;gap:6px}
  main{padding:30px 0 56px}
}
@media(max-width:380px){
  .brand{font-size:14px}
  nav a{margin-left:8px;font-size:12px}
}
@media print{
  header,footer,nav{display:none}
  .toc{break-inside:avoid}
  main{padding:0}
  body{font-size:12px}
}