:root{
  --paper:#f5f6f2;
  --surface:#fff;
  --surface-soft:#eef5f1;
  --ink:#15222e;
  --muted:#52616d;
  --line:#dce2dc;
  --accent:#0b7a55;
  --accent-strong:#086747;
  --warning:#fff6df;
  --warning-line:#ddc47a;
  --danger:#9b3439;
  --radius-card:16px;
  --radius-control:9px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--paper);color:var(--ink);font-family:"PingFang SC","Microsoft YaHei","Noto Sans CJK SC",system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.75}
a{color:var(--accent)}
a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid rgba(14,159,110,.28);outline-offset:3px}
.skip{position:absolute;left:-9999px;top:8px;background:var(--ink);color:#fff;padding:8px 12px;border-radius:var(--radius-control);z-index:20}.skip:focus{left:12px}
.site-head{position:sticky;top:0;z-index:10;background:rgba(245,246,242,.94);backdrop-filter:blur(12px);border-bottom:1px solid var(--line)}
.head-inner{max-width:1160px;height:68px;margin:auto;padding:0 24px;display:flex;align-items:center;justify-content:space-between;gap:24px}
.brand{font-family:"Noto Serif SC",Georgia,serif;font-weight:900;font-size:20px;color:var(--ink);text-decoration:none}.brand span{color:var(--accent)}
.site-nav{display:flex;align-items:center;gap:5px;white-space:nowrap}.site-nav a{color:var(--ink);font-size:13px;font-weight:700;text-decoration:none;padding:8px 11px;border-radius:var(--radius-control)}.site-nav a:hover,.site-nav a[aria-current="page"]{background:var(--surface-soft);color:var(--accent)}
.page{max-width:1160px;margin:auto;padding:44px 24px 72px}
.crumbs{display:flex;gap:7px;flex-wrap:wrap;font-size:12px;color:var(--muted);margin-bottom:22px}.crumbs a{text-decoration:none}.crumbs span+span:before{content:"/";margin-right:7px;color:#9aa5a0}
.article-grid{display:grid;grid-template-columns:minmax(0,760px) 280px;gap:56px;align-items:start}
.article-hero{padding:8px 0 28px;border-bottom:1px solid var(--line);margin-bottom:30px}.article-hero .kicker{font-size:12px;font-weight:900;letter-spacing:.12em;color:var(--accent);margin-bottom:9px}.article-hero h1{font-family:"Noto Serif SC",Georgia,serif;font-size:clamp(31px,5vw,48px);line-height:1.2;letter-spacing:-.025em;margin:0 0 15px}.article-hero .lead{font-size:17px;color:var(--muted);max-width:64ch;margin:0}.article-meta{display:flex;gap:12px;flex-wrap:wrap;margin-top:18px;font-size:11px;color:var(--muted)}
.answer{background:var(--ink);color:#edf7f2;border-radius:var(--radius-card);padding:22px 24px;margin:0 0 30px}.answer b{display:block;color:#76d6b4;margin-bottom:6px}.answer p{margin:0;color:#e8efec}
.content h2{font-family:"Noto Serif SC",Georgia,serif;font-size:27px;line-height:1.35;margin:42px 0 14px}.content h3{font-size:17px;margin:26px 0 9px}.content p,.content li{font-size:15px;color:#344650}.content ul,.content ol{padding-left:23px}.content li{margin:8px 0}.content strong{color:var(--ink)}
.callout{border-left:4px solid var(--accent);background:var(--surface-soft);padding:16px 18px;border-radius:0 var(--radius-control) var(--radius-control) 0;margin:22px 0}.callout.warning{border-color:var(--warning-line);background:var(--warning)}.callout.danger{border-color:#db8e92;background:#fff0f0}.callout p{margin:4px 0 0}
.formula{background:#13242f;color:#f0f7f4;border-radius:var(--radius-card);padding:20px 22px;margin:20px 0;font-family:ui-monospace,SFMono-Regular,Menlo,monospace;overflow:auto}.formula strong{color:#7ad8b8}.formula small{display:block;color:#b8c7c1;margin-top:8px;font-family:inherit}
.compare{width:100%;border-collapse:separate;border-spacing:0;margin:20px 0;border:1px solid var(--line);border-radius:var(--radius-card);overflow:hidden;background:var(--surface)}.compare th,.compare td{text-align:left;padding:13px 15px;border-bottom:1px solid var(--line);vertical-align:top;font-size:13px}.compare tr:last-child td{border-bottom:0}.compare th{background:#edf3ef;font-size:12px;color:var(--ink)}
.checklist{display:grid;grid-template-columns:1fr 1fr;gap:10px;padding:0;list-style:none}.checklist li{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-control);padding:13px 15px;margin:0}
.side{position:sticky;top:92px;display:grid;gap:14px}.side-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-card);padding:18px}.side-card h2{font:900 16px "Noto Serif SC",Georgia,serif;margin:0 0 10px}.side-card p{font-size:12px;color:var(--muted);margin:0 0 12px}.side-card nav{display:grid;gap:4px}.side-card nav a{font-size:12px;text-decoration:none;padding:7px 8px;border-radius:7px}.side-card nav a:hover{background:var(--surface-soft)}
.primary,.secondary{display:inline-flex;min-height:43px;align-items:center;justify-content:center;padding:10px 16px;border-radius:var(--radius-control);font:800 13px inherit;text-decoration:none;white-space:nowrap;transition:transform .15s,background .15s}.primary{background:var(--ink);color:#fff}.primary:hover{background:var(--accent-strong);color:#fff}.secondary{border:1px solid var(--line);background:var(--surface);color:var(--ink)}.primary:active,.secondary:active,button:active{transform:translateY(1px)}
.next-box{margin-top:44px;padding:24px;background:var(--surface-soft);border:1px solid #cfe1d8;border-radius:var(--radius-card)}.next-box h2{margin:0 0 8px;font-size:23px}.next-box p{margin:0 0 16px}.actions{display:flex;gap:10px;flex-wrap:wrap}
.hub-hero{max-width:830px;padding:30px 0 40px}.hub-hero h1{font:900 clamp(34px,6vw,58px)/1.16 "Noto Serif SC",Georgia,serif;letter-spacing:-.035em;margin:0 0 16px}.hub-hero p{font-size:17px;color:var(--muted);max-width:64ch}.hub-grid{display:grid;grid-template-columns:1.25fr .75fr;gap:16px}.hub-group{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-card);padding:24px}.hub-group:first-child{grid-row:span 2}.hub-group h2{font:900 24px "Noto Serif SC",Georgia,serif;margin:0 0 7px}.hub-group>p{color:var(--muted);font-size:13px;margin:0 0 20px}.link-grid{display:grid;grid-template-columns:1fr 1fr;gap:9px}.topic-link{display:block;padding:14px;border-radius:var(--radius-control);background:#f7f9f6;border:1px solid var(--line);text-decoration:none;color:var(--ink)}.topic-link:hover{border-color:var(--accent);background:var(--surface-soft)}.topic-link b{display:block;font-size:14px}.topic-link span{display:block;font-size:11px;color:var(--muted);margin-top:3px}.hub-group:not(:first-child) .link-grid{grid-template-columns:1fr}
.calculator{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-card);padding:24px;margin:24px 0}.calculator h2{margin:0 0 6px}.calculator>p{margin:0 0 20px;color:var(--muted)}.form-grid{display:grid;grid-template-columns:1fr 1fr;gap:14px}.field{display:grid;gap:5px}.field label{font-size:12px;font-weight:800;color:var(--ink)}.field small{font-size:10px;color:var(--muted)}.field input,.field select{width:100%;border:1px solid #b8c3bd;border-radius:var(--radius-control);background:var(--surface);color:var(--ink);padding:10px 11px;font:inherit}.calc-button{border:0;border-radius:var(--radius-control);background:var(--ink);color:#fff;padding:11px 18px;font:800 13px inherit;cursor:pointer;margin-top:16px}.results{display:grid;grid-template-columns:repeat(2,1fr);gap:10px;margin-top:18px}.result{background:var(--surface-soft);border-radius:var(--radius-control);padding:14px}.result span{display:block;color:var(--muted);font-size:10px}.result strong{display:block;font-size:20px;margin-top:3px}.result.wide{grid-column:1/-1}.calc-note{margin-top:12px;font-size:11px;color:var(--muted)}
.quiz{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-card);padding:20px;margin:30px 0}.quiz h2{margin:0 0 7px;font-size:21px}.quiz p{margin:0 0 12px}.quiz-options{display:grid;gap:7px}.quiz button{border:1px solid var(--line);background:var(--surface);color:var(--ink);text-align:left;border-radius:var(--radius-control);padding:10px 12px;font:inherit;cursor:pointer}.quiz button:hover{border-color:var(--accent)}.quiz button.correct{background:#e2f4ec;border-color:#69b895;color:#086747}.quiz button.wrong{background:#fff0f0;border-color:#d89498;color:var(--danger)}.quiz-feedback{min-height:24px;margin-top:9px;font-size:12px;font-weight:700}
.source-list{font-size:12px;color:var(--muted)}.source-list a{overflow-wrap:anywhere}
.site-foot{border-top:1px solid var(--line);padding:28px 24px;color:var(--muted);font-size:11px}.foot-inner{max-width:1160px;margin:auto;display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap}.foot-inner a{text-decoration:none}
@media(max-width:900px){.article-grid{grid-template-columns:1fr}.side{position:static;grid-template-columns:1fr 1fr}.hub-grid{grid-template-columns:1fr}.hub-group:first-child{grid-row:auto}}
@media(max-width:700px){.head-inner{height:auto;min-height:64px;padding:10px 15px;align-items:flex-start}.site-nav{max-width:72vw;overflow-x:auto;padding-bottom:3px}.site-nav a{min-height:44px;display:flex;align-items:center}.page{padding:28px 15px 52px}.article-hero h1{font-size:34px}.article-hero .lead{font-size:15px}.checklist,.form-grid,.results,.link-grid,.side{grid-template-columns:1fr}.hub-group{padding:19px}.actions{display:grid}.primary,.secondary{width:100%}.compare{display:block;overflow-x:auto}.foot-inner{display:grid}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{transition:none!important}}