:root{
  --sb-w:300px; --text:#1f2328; --muted:#656d76; --line:#e5e7eb; --bg:#fff; --sb-bg:#f7f8fa;
  --accent:#2f6fde; --accent-bg:#e8f0fd; --code-bg:#f6f8fa; --quote-bg:#f4f8ff;
  --font:-apple-system,BlinkMacSystemFont,"PingFang SC","Hiragino Sans GB","Noto Sans CJK SC","Noto Sans SC","Source Han Sans SC","Microsoft YaHei","WenQuanYi Micro Hei","Helvetica Neue",Arial,sans-serif;
  --mono:"SFMono-Regular",Menlo,Consolas,"Liberation Mono","Noto Sans Mono CJK SC",monospace;
}
*{box-sizing:border-box}
html{scroll-padding-top:20px}
body{margin:0;font-family:var(--font);color:var(--text);background:var(--bg);font-size:16px;line-height:1.8;-webkit-font-smoothing:antialiased}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}

/* sidebar */
.sidebar{position:fixed;top:0;left:0;bottom:0;width:var(--sb-w);background:var(--sb-bg);border-right:1px solid var(--line);overflow-y:auto;padding:22px 14px 40px;z-index:30}
.brand{display:block;padding:4px 10px 18px;margin-bottom:10px;border-bottom:1px solid var(--line);color:var(--text)}
.brand:hover{text-decoration:none}
.brand-kicker{display:block;font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--accent);font-weight:600}
.brand-title{display:block;font-size:18px;font-weight:700;line-height:1.4;margin-top:4px}
.articles,.toc{list-style:none;margin:0;padding:0}
.articles>li{margin:2px 0}
.art{display:flex;gap:8px;padding:7px 10px;border-radius:6px;color:#343a40;font-size:14px;line-height:1.5}
.art:hover{background:#eceef2;text-decoration:none}
.art .num{flex:none;font-variant-numeric:tabular-nums;color:var(--muted);font-weight:600;width:20px}
.articles>li.active>.art{background:var(--accent-bg);color:var(--accent);font-weight:600}
.articles>li.active>.art .num{color:var(--accent)}
.toc{margin:4px 0 10px 19px;border-left:1px solid #d8dde4}
.toc li a{display:block;padding:3px 10px 3px 12px;font-size:13px;line-height:1.5;color:var(--muted);border-left:2px solid transparent;margin-left:-1px}
.toc li.l3 a{padding-left:26px;font-size:12.5px}
.toc li a:hover{color:var(--text);text-decoration:none}
.toc li a.current{color:var(--accent);border-left-color:var(--accent);font-weight:500}

/* main */
.main{margin-left:var(--sb-w);min-height:100vh}
.hero{width:100%;max-height:340px;overflow:hidden;background:#eef1f5;border-bottom:1px solid var(--line)}
.hero img{display:block;width:100%;height:340px;object-fit:cover}
.content{max-width:760px;margin:0 auto;padding:36px 28px 40px}
.page-title{font-size:30px;line-height:1.35;margin:0 0 24px;letter-spacing:.01em}
.content h2{font-size:23px;line-height:1.4;margin:2.2em 0 .8em;padding-bottom:.35em;border-bottom:1px solid var(--line)}
.content h3{font-size:18.5px;margin:1.8em 0 .6em}
.content h4{font-size:16px;margin:1.5em 0 .5em}
.content p{margin:.85em 0}
.content ul,.content ol{padding-left:1.6em;margin:.8em 0}
.content li{margin:.3em 0}
.content strong{font-weight:650}
.content hr{border:0;border-top:1px solid var(--line);margin:2em 0}
.content code{font-family:var(--mono);font-size:.88em;background:var(--code-bg);border:1px solid #eaecef;border-radius:4px;padding:.1em .35em}
.content pre{background:var(--code-bg);border:1px solid var(--line);border-radius:8px;padding:14px 16px;overflow-x:auto;line-height:1.6;font-size:13.5px}
.content pre code{background:none;border:0;padding:0;font-size:inherit;white-space:pre}
blockquote{margin:1.2em 0;padding:.6em 1.1em;border-left:4px solid var(--accent);background:var(--quote-bg);border-radius:0 8px 8px 0;color:#334}
blockquote p{margin:.4em 0}
blockquote.callout{font-size:15.5px}
.table-wrap{overflow-x:auto;margin:1.2em 0;border:1px solid var(--line);border-radius:8px}
table{border-collapse:collapse;width:100%;font-size:14.5px;line-height:1.65}
th,td{border-bottom:1px solid var(--line);padding:8px 12px;text-align:left;vertical-align:top}
td+td,th+th{border-left:1px solid var(--line)}
thead th{background:#f3f5f8;font-weight:600;white-space:nowrap}
tbody tr:last-child td{border-bottom:0}
tbody tr:nth-child(even) td{background:#fbfcfd}
.fig{margin:1.8em 0;text-align:center}
.fig img{max-width:100%;height:auto;border-radius:6px;border:1px solid #eef0f3;background:#fff}
.fig figcaption{margin-top:.5em;font-size:13.5px;color:var(--muted)}
.page-cards{list-style:none;padding:0 !important;display:grid;grid-template-columns:1fr 1fr;gap:10px}
.page-cards li{margin:0}
.page-cards a{display:flex;gap:10px;height:100%;padding:12px 14px;border:1px solid var(--line);border-radius:8px;color:var(--text);font-size:14.5px;line-height:1.55;transition:border-color .15s,box-shadow .15s}
.page-cards a:hover{border-color:var(--accent);box-shadow:0 2px 8px rgba(47,111,222,.1);text-decoration:none}
.page-cards .num{color:var(--accent);font-weight:700}
.pager{display:grid;grid-template-columns:1fr 1fr;gap:14px;margin-top:56px;padding-top:24px;border-top:1px solid var(--line)}
.pager a{display:block;padding:12px 16px;border:1px solid var(--line);border-radius:8px;color:var(--text);line-height:1.5}
.pager a:hover{border-color:var(--accent);text-decoration:none}
.pager small{display:block;color:var(--muted);font-size:12.5px}
.pager span{color:var(--accent);font-weight:500;font-size:14.5px}
.pager .next{text-align:right;grid-column:2}
.foot{max-width:760px;margin:0 auto;padding:16px 28px 40px;color:#9aa1a9;font-size:13px}

/* topbar (mobile) */
.topbar{display:none}
.overlay{display:none}
@media (max-width:900px){
  .topbar{display:flex;align-items:center;gap:10px;position:sticky;top:0;z-index:20;height:52px;padding:0 12px;background:rgba(255,255,255,.96);border-bottom:1px solid var(--line);backdrop-filter:blur(6px)}
  .topbar-title{color:var(--text);font-weight:600;font-size:15px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
  .menu-btn{width:38px;height:38px;border:1px solid var(--line);border-radius:8px;background:#fff;display:flex;flex-direction:column;justify-content:center;align-items:center;gap:4px;cursor:pointer;padding:0}
  .menu-btn span{display:block;width:18px;height:2px;background:#333;border-radius:1px}
  html{scroll-padding-top:64px}
  .sidebar{transform:translateX(-100%);transition:transform .22s ease;width:min(84vw,320px);box-shadow:none}
  body.nav-open .sidebar{transform:none;box-shadow:4px 0 24px rgba(0,0,0,.15)}
  body.nav-open .overlay{display:block;position:fixed;inset:0;background:rgba(0,0,0,.3);z-index:25}
  .main{margin-left:0}
  .hero img{height:200px}
  .content{padding:24px 18px 32px}
  .page-title{font-size:24px}
  .content h2{font-size:20px}
  .page-cards{grid-template-columns:1fr}
  .pager{grid-template-columns:1fr}
  .pager .next{grid-column:1}
}
@media print{.sidebar,.topbar,.pager{display:none}.main{margin:0}}