:root{
  --bg:#f6f8fb; --surface:#ffffff; --surface-2:#eef2f8;
  --text:#1c2430; --muted:#5b6675; --border:#e2e8f0;
  --primary:#3b4fe0; --primary-d:#2c3bb0; --accent:#0fb5a6;
  --warn:#b8860b; --radius:14px; --shadow:0 6px 24px rgba(28,36,48,.08);
  --maxw:1080px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  background:var(--bg);color:var(--text);line-height:1.7;font-size:16px;-webkit-font-smoothing:antialiased}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 20px}
.btn{display:inline-flex;align-items:center;gap:8px;padding:11px 20px;border-radius:10px;font-weight:600;
  font-size:15px;cursor:pointer;border:1px solid transparent;transition:.15s;text-decoration:none}
.btn:hover{text-decoration:none;transform:translateY(-1px)}
.btn-primary{background:var(--primary);color:#fff}
.btn-primary:hover{background:var(--primary-d)}
.btn-ghost{background:var(--surface);color:var(--text);border-color:var(--border)}
.btn-ghost:hover{border-color:var(--primary);color:var(--primary)}
.btn-accent{background:var(--accent);color:#fff}
.btn-lg{padding:14px 26px;font-size:16px}

/* top nav */
.nav{position:sticky;top:0;z-index:40;background:rgba(255,255,255,.85);backdrop-filter:blur(10px);
  border-bottom:1px solid var(--border)}
.nav-inner{display:flex;align-items:center;gap:18px;height:60px}
.logo{font-weight:800;font-size:18px;letter-spacing:.3px;color:var(--text);display:flex;align-items:center;gap:8px}
.logo .dot{width:10px;height:10px;border-radius:50%;background:var(--accent)}
.nav a.navlink{color:var(--muted);font-size:14.5px;font-weight:500}
.nav a.navlink:hover{color:var(--primary)}
.nav .spacer{flex:1}
.nav .menu-btn{display:none;background:none;border:1px solid var(--border);border-radius:8px;padding:6px 10px;font-size:18px;cursor:pointer}
@media(max-width:760px){
  .nav .navlink{display:none}
  .nav .menu-btn{display:inline-block}
  .nav .mobile{display:flex;flex-direction:column;gap:10px;padding:14px 20px;border-bottom:1px solid var(--border);background:var(--surface)}
}

/* disclaimer top strip */
.strip{background:var(--surface-2);color:var(--muted);font-size:13px;text-align:center;padding:7px 14px;border-bottom:1px solid var(--border)}

/* hero */
.hero{background:linear-gradient(135deg,#eef1fe 0%,#e9fbf8 100%);padding:60px 0 50px}
.hero h1{font-size:clamp(28px,5vw,44px);margin:0 0 14px;line-height:1.2;font-weight:800}
.hero p.sub{font-size:18px;color:var(--muted);margin:0 0 26px;max-width:640px}
.hero .cta{display:flex;gap:14px;flex-wrap:wrap}
.badge{display:inline-block;background:#fff;border:1px solid var(--border);color:var(--primary);
  font-size:13px;font-weight:600;padding:5px 12px;border-radius:999px;margin-bottom:18px}

/* sections */
section.block{padding:54px 0}
.section-head{margin-bottom:26px}
.section-head h2{font-size:26px;margin:0 0 8px;font-weight:800}
.section-head p{color:var(--muted);margin:0;max-width:680px}
.grid{display:grid;gap:18px}
.grid.cols-2{grid-template-columns:repeat(2,1fr)}
.grid.cols-3{grid-template-columns:repeat(3,1fr)}
.grid.cols-4{grid-template-columns:repeat(4,1fr)}
@media(max-width:860px){.grid.cols-3,.grid.cols-4{grid-template-columns:repeat(2,1fr)}}
@media(max-width:560px){.grid.cols-2,.grid.cols-3,.grid.cols-4{grid-template-columns:1fr}}
.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:22px;
  box-shadow:var(--shadow);transition:.15s}
.card:hover{transform:translateY(-3px);border-color:#cdd6e6}
.card .ico{font-size:26px}
.card h3{margin:12px 0 8px;font-size:18px}
.card p{color:var(--muted);font-size:14.5px;margin:0 0 14px}
.card .more{font-weight:600;font-size:14px}

/* article layout */
.article{display:grid;grid-template-columns:1fr 220px;gap:36px;padding:40px 0 80px}
.article .prose{max-width:720px}
.article h1{font-size:32px;margin:0 0 6px;font-weight:800}
.article .meta{color:var(--muted);font-size:13.5px;margin-bottom:26px}
.article h2{font-size:23px;margin:38px 0 12px;font-weight:700;scroll-margin-top:80px}
.article h3{font-size:18px;margin:26px 0 8px;font-weight:700}
.article p{margin:12px 0}
.article ul,.article ol{padding-left:22px;margin:12px 0}
.article li{margin:6px 0}
.article code{background:var(--surface-2);padding:2px 6px;border-radius:6px;font-size:13.5px;
  font-family:ui-monospace,SFMono-Regular,Menlo,monospace}
.article pre{background:#1c2430;color:#e6edf3;padding:16px;border-radius:10px;overflow:auto;font-size:13.5px}
.article pre code{background:none;color:inherit;padding:0}
.article blockquote{margin:18px 0;padding:12px 18px;border-left:4px solid var(--accent);
  background:var(--surface-2);border-radius:0 8px 8px 0;color:var(--muted)}
.toc{position:sticky;top:80px;align-self:start;font-size:14px}
.toc .t-title{font-weight:700;margin-bottom:10px;color:var(--muted);font-size:13px;text-transform:uppercase;letter-spacing:.5px}
.toc a{display:block;color:var(--muted);padding:5px 0;border-left:2px solid transparent;padding-left:12px}
.toc a:hover,.toc a.active{color:var(--primary);border-left-color:var(--primary);text-decoration:none}
@media(max-width:860px){.article{grid-template-columns:1fr}.toc{display:none}}

/* manual mirrored content (.vp-doc from bluebook) */
.vp-doc{word-break:break-word}
.vp-doc hr{border:none;border-top:1px solid var(--border);margin:30px 0}
.vp-doc img{border:1px solid var(--border);border-radius:12px;box-shadow:var(--shadow);
  margin:10px 0;display:block}
.vp-doc figure{margin:24px 0;text-align:center}
.vp-doc figure img{display:inline-block;border:1px solid var(--border);border-radius:12px;
  box-shadow:var(--shadow)}
.vp-doc figcaption{color:var(--muted);font-size:13px;margin-top:8px}
.vp-doc table{width:100%;border-collapse:collapse;margin:20px 0;font-size:14.5px;
  display:block;overflow-x:auto;max-width:100%}
.vp-doc th,.vp-doc td{border:1px solid var(--border);padding:9px 12px;text-align:left;
  vertical-align:top;white-space:normal}
.vp-doc thead th{background:var(--surface-2);font-weight:700}
.vp-doc tbody tr:nth-child(even){background:#fafbfe}
.vp-doc .wb-mermaid__fallback{margin:20px 0;border-radius:10px;overflow:auto}
.vp-doc .header-anchor{color:var(--border);font-weight:400;margin-left:6px;opacity:0}
.vp-doc h2:hover .header-anchor,.vp-doc h3:hover .header-anchor{opacity:1}

/* homepage manual chapters nav */
.parts{display:grid;gap:22px}
.part{border:1px solid var(--border);border-radius:var(--radius);background:var(--surface);
  padding:20px 22px;box-shadow:var(--shadow)}
.part h3{margin:0 0 12px;font-size:18px;display:flex;align-items:center;gap:8px}
.part h3 .tag{font-size:12px;font-weight:600;color:var(--accent);background:var(--surface-2);
  border:1px solid var(--border);padding:2px 9px;border-radius:999px}
.ch-list{list-style:none;margin:0;padding:0;display:grid;
  grid-template-columns:repeat(2,1fr);gap:8px 18px}
.ch-list li a{display:block;color:var(--text);font-size:14.5px;padding:7px 10px;border-radius:8px;
  border:1px solid transparent;transition:.15s}
.ch-list li a:hover{background:var(--surface-2);border-color:var(--border);color:var(--primary);
  text-decoration:none}
@media(max-width:680px){.ch-list{grid-template-columns:1fr}}

/* callout card inside article (conversion) */
.promo{background:linear-gradient(135deg,#eef1fe,#e9fbf8);border:1px solid #d6def5;border-radius:var(--radius);
  padding:22px;margin:26px 0;display:flex;gap:18px;align-items:center;flex-wrap:wrap}
.promo .qr{width:120px;height:120px;background:#fff;border:1px solid var(--border);border-radius:10px;padding:6px}
.promo h4{margin:0 0 6px;font-size:17px}
.promo p{margin:0 0 12px;color:var(--muted);font-size:14px}
.promo .code{font-family:ui-monospace,monospace;background:#fff;border:1px dashed var(--primary);
  padding:6px 12px;border-radius:8px;font-weight:700;letter-spacing:1px}

/* step list for download page */
.steps{counter-reset:step;padding:0;margin:22px 0;list-style:none}
.steps li{position:relative;padding:14px 16px 14px 56px;background:var(--surface);border:1px solid var(--border);
  border-radius:10px;margin-bottom:12px}
.steps li::before{counter-increment:step;content:counter(step);position:absolute;left:14px;top:14px;
  width:28px;height:28px;border-radius:50%;background:var(--primary);color:#fff;font-weight:700;
  display:flex;align-items:center;justify-content:center;font-size:14px}
.steps li b{display:block;margin-bottom:2px}

/* footer */
.footer{background:#11151c;color:#aeb6c2;padding:44px 0 30px;font-size:14px;margin-top:40px}
.footer a{color:#cdd6e6}
.footer .cols{display:grid;grid-template-columns:1.4fr 1fr 1fr 1fr;gap:28px}
.footer h4{color:#fff;font-size:14px;margin:0 0 14px}
.footer ul{list-style:none;padding:0;margin:0}
.footer li{margin:8px 0}
.footer .bottom{border-top:1px solid #232a35;margin-top:30px;padding-top:18px;color:#7c8696;font-size:13px}
@media(max-width:760px){.footer .cols{grid-template-columns:1fr 1fr}}

/* sticky invite bar (injected by JS) */
.invite-bar{position:fixed;left:0;right:0;bottom:0;z-index:50;background:#11151c;color:#fff;
  display:flex;align-items:center;gap:14px;padding:12px 18px;box-shadow:0 -6px 24px rgba(0,0,0,.18);flex-wrap:wrap}
.invite-bar .ib-tag{font-size:12.5px;color:#9aa4b2}
.invite-bar .ib-code{font-family:ui-monospace,monospace;font-weight:700;letter-spacing:1px;
  background:#1f2733;padding:6px 12px;border-radius:8px;border:1px solid #2c3645}
.invite-bar .ib-actions{margin-left:auto;display:flex;gap:10px;flex-wrap:wrap}
.invite-bar .btn{padding:9px 16px;font-size:14px}
.ib-close{background:none;border:none;color:#7c8696;font-size:20px;cursor:pointer;line-height:1}
@media(max-width:560px){.invite-bar .ib-tag{display:none}.invite-bar .ib-actions{width:100%;margin-left:0}}
.toast{position:fixed;bottom:80px;left:50%;transform:translateX(-50%);background:var(--accent);color:#fff;
  padding:10px 20px;border-radius:10px;font-size:14px;font-weight:600;opacity:0;transition:.25s;z-index:60;pointer-events:none}
.toast.show{opacity:1}