:root{
  --bg:#fbfaf7;
  --paper:#ffffff;
  --ink:#1f2328;
  --ink-soft:#5b626b;
  --line:#e7e3da;
  --brand:#e11d48;
  --brand-soft:#fff1f3;
  --blue:#2563eb;
  --green:#16a34a;
  --amber:#d97706;
  --purple:#7c3aed;
  --code-bg:#1e2430;
  --code-ink:#e6edf3;
  --maxw:800px;
}
*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  background:var(--bg);
  color:var(--ink);
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  line-height:1.85;
  font-size:17px;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--brand);text-decoration:none;}
a:hover{text-decoration:underline;}

/* top bar */
.topbar{
  position:sticky;top:0;z-index:10;
  background:rgba(255,255,255,.92);
  backdrop-filter:blur(8px);
  border-bottom:1px solid var(--line);
  display:flex;align-items:center;justify-content:space-between;
  padding:11px 22px;
}
.topbar .brand{font-weight:700;color:var(--ink);font-size:15px;}
.topbar .brand small{color:var(--ink-soft);font-weight:400;margin-left:8px;font-size:12px;}
.topbar .nav{font-size:14px;font-weight:600;}

.wrap{max-width:var(--maxw);margin:0 auto;padding:30px 22px 80px;}

/* cover */
.cover{text-align:center;padding:54px 20px 30px;}
.cover h1{font-size:42px;line-height:1.25;margin:0 0 10px;letter-spacing:.5px;}
.cover .sub{color:var(--ink-soft);font-size:18px;letter-spacing:.4px;}
.meta{max-width:640px;margin:28px auto 0;text-align:left;
  background:var(--paper);border:1px solid var(--line);border-radius:14px;padding:16px 22px;}
.meta div{display:flex;gap:10px;padding:5px 0;border-bottom:1px dashed var(--line);}
.meta div:last-child{border-bottom:none;}
.meta .k{color:var(--ink-soft);min-width:88px;flex:none;font-size:14px;}
.meta .v{color:var(--ink);font-size:14px;}

/* TOC */
.toc{margin-top:40px;}
.part{margin-top:32px;}
.part h2{font-size:14px;text-transform:uppercase;letter-spacing:1.6px;color:var(--brand);
  border-left:4px solid var(--brand);padding-left:10px;margin:0 0 14px;}
.chapter-list{list-style:none;margin:0;padding:0;display:grid;gap:10px;}
.chapter-list a{
  display:flex;align-items:baseline;gap:12px;
  background:var(--paper);border:1px solid var(--line);border-radius:12px;
  padding:14px 18px;color:var(--ink);
  transition:transform .12s ease,box-shadow .12s ease,border-color .12s ease;
}
.chapter-list a:hover{border-color:var(--brand);text-decoration:none;transform:translateY(-1px);box-shadow:0 6px 18px rgba(0,0,0,.06);}
.chapter-list .no{font-weight:700;color:var(--brand);font-variant-numeric:tabular-nums;min-width:40px;flex:none;}
.chapter-list .tt{flex:1;font-weight:600;}
.chapter-list .desc{display:block;color:var(--ink-soft);font-size:13px;font-weight:400;margin-top:2px;}

/* chapter page */
.part-tag{color:var(--brand);font-size:14px;font-weight:600;letter-spacing:.5px;}
.chapter-title{font-size:30px;line-height:1.3;margin:6px 0 4px;}
h3{font-size:20px;margin:34px 0 10px;border-left:3px solid var(--brand);padding-left:10px;}
p{margin:14px 0;}
ul,ol{margin:14px 0;padding-left:24px;}
li{margin:6px 0;}

/* code */
pre{background:var(--code-bg);color:var(--code-ink);border-radius:12px;padding:16px 18px;overflow:auto;font-size:14px;line-height:1.6;position:relative;margin:18px 0;}
pre[data-lang]::before{content:attr(data-lang);position:absolute;top:8px;right:12px;font-size:11px;color:#8b98a8;letter-spacing:.5px;text-transform:uppercase;}
code{font-family:"JetBrains Mono",Menlo,Consolas,monospace;}
:not(pre) > code{background:#f1efe9;border:1px solid var(--line);border-radius:6px;padding:1px 6px;font-size:.88em;color:#b4243a;}

/* tables */
table{border-collapse:collapse;width:100%;margin:18px 0;font-size:15px;background:var(--paper);border:1px solid var(--line);border-radius:10px;overflow:hidden;}
th,td{border:1px solid var(--line);padding:10px 12px;text-align:left;vertical-align:top;}
thead th{background:#f6f4ef;font-weight:700;}
tbody tr:nth-child(even){background:#fcfbf8;}

/* callouts */
.callout{border-radius:12px;padding:14px 18px;margin:20px 0;border:1px solid var(--line);border-left:5px solid var(--blue);background:#f7f9ff;}
.callout .ct{font-weight:700;margin-bottom:4px;color:var(--blue);}
.callout p{margin:6px 0;}
.callout.advice{border-left-color:var(--green);background:#f3fbf5;}
.callout.advice .ct{color:var(--green);}
.callout.warn{border-left-color:var(--amber);background:#fffaf0;}
.callout.warn .ct{color:var(--amber);}
.callout.summary{border-left-color:var(--purple);background:#faf7ff;}
.callout.summary .ct{color:var(--purple);}

/* bridge */
.bridge{margin:28px 0;padding:14px 18px;border-radius:12px;background:var(--brand-soft);color:#9f1239;font-weight:600;border:1px dashed #f3a9b8;}

/* pager */
.pager{display:flex;justify-content:space-between;gap:12px;margin-top:46px;padding-top:20px;border-top:1px solid var(--line);}
.pager a{flex:1;background:var(--paper);border:1px solid var(--line);border-radius:12px;padding:12px 16px;color:var(--ink);}
.pager a:hover{border-color:var(--brand);text-decoration:none;transform:translateY(-1px);}
.pager .next{text-align:right;}
.pager .lbl{display:block;font-size:12px;color:var(--ink-soft);}
.pager .pg-tt{font-weight:700;color:var(--brand);}

footer{text-align:center;color:var(--ink-soft);font-size:13px;padding:28px 20px 50px;line-height:1.7;}

@media (max-width:600px){
  .cover h1{font-size:30px;}
  body{font-size:16px;}
  .chapter-list a{flex-direction:column;gap:3px;}
  .meta .k{min-width:0;}
}