:root{
  --bg:#f6f7f9; --paper:#ffffff; --ink:#1f2937; --muted:#5f6b7a; --soft:#f3f5f8;
  --line:#d8dee8; --line-soft:#e8edf3; --accent:#315f8f; --accent-2:#1f6f5b;
  --warn-bg:#fff8e6; --warn-line:#ead18a; --code:#f4f6f8; --max:1200px;
}
*{box-sizing:border-box} html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Inter,Arial,sans-serif;line-height:1.68;font-size:16px}
a{color:#245c96;text-decoration-thickness:.07em;text-underline-offset:.18em} a:hover{color:#163f69;text-decoration-thickness:.13em}
.wrap{width:min(var(--max),94%);margin-inline:auto}.top{background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20;box-shadow:0 1px 2px rgba(15,23,42,.03)}
.nav{display:flex;align-items:center;justify-content:space-between;gap:20px;min-height:62px}.brand{display:flex;align-items:center;gap:10px;color:var(--ink);font-weight:700;text-decoration:none;letter-spacing:-.01em}.mark{display:grid;place-items:center;width:32px;height:32px;border:1px solid #bdc8d6;border-radius:7px;background:linear-gradient(180deg,#fff,#eef3f8);color:#214b73;font-size:.78rem;font-weight:800}.links{display:flex;gap:3px;align-items:center;flex-wrap:wrap}.links a{color:#344054;text-decoration:none;font-weight:600;font-size:.94rem;padding:8px 10px;border-radius:8px}.links a:hover{background:#f1f5f9}.links a.cta{background:#eef5fb;color:#17446f;border:1px solid #d2e2f0}
.hero{padding:44px 0 30px;background:#fff;border-bottom:1px solid var(--line)}.hero-grid{display:grid;grid-template-columns:minmax(0,1.1fr) 340px;gap:30px;align-items:center}.eyebrow,.small{color:#46627f;text-transform:uppercase;letter-spacing:.12em;font-weight:800;font-size:.76rem}.hero h1,h1{font-size:clamp(2rem,4.5vw,3.45rem);line-height:1.08;margin:.18em 0 .28em;letter-spacing:-.04em}h2{font-size:1.55rem;line-height:1.25;margin:2.05em 0 .55em;letter-spacing:-.02em;border-top:1px solid var(--line-soft);padding-top:1.1em}h3{font-size:1.08rem;margin:1.45em 0 .35em}.lede,.subtitle{font-size:1.12rem;color:#4b5563;max-width:780px}.note{font-size:.92rem;color:var(--muted)}
.searchbox,.note-card{background:#f8fafc;border:1px solid var(--line);border-radius:12px;padding:16px}.searchbox input{width:100%;border:1px solid var(--line);border-radius:8px;padding:12px;font-size:1rem;background:#fff}.chips{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}.chip,.pill,.badge,.bubble{display:inline-block;background:#f3f7fb;border:1px solid #d8e5f1;color:#294d70;border-radius:999px;padding:5px 9px;font-weight:700;font-size:.82rem}
.section{padding:24px 0}.grid,.card-grid,.directory{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.grid.two,.callout-row{grid-template-columns:repeat(2,minmax(0,1fr))}.card,.panel,.glossary,.decision-box{background:#fff;border:1px solid var(--line);border-radius:12px;padding:18px;box-shadow:0 1px 2px rgba(15,23,42,.035)}.card h3,.panel h2{margin-top:0}.card p,.panel p{color:#53606f;margin-bottom:0}.panel{display:block;text-decoration:none;color:var(--ink)}
.layout{display:grid;grid-template-columns:255px minmax(0,1fr);gap:26px;align-items:start;padding-top:26px}.side{position:sticky;top:82px;background:#fff;border:1px solid var(--line);border-radius:12px;padding:14px;font-size:.93rem}.side strong{display:block;margin:0 0 8px}.side a{display:block;color:#475467;text-decoration:none;padding:7px 0;border-top:1px solid var(--line-soft)}.side a:hover{color:#17446f}.article{background:#fff;border:1px solid var(--line);border-radius:14px;padding:clamp(22px,4vw,44px);max-width:900px}.article p{max-width:76ch}.article ul,.article ol{padding-left:1.35rem}.article li{margin:.35em 0}.article-meta{color:var(--muted);font-size:.92rem;border-bottom:1px solid var(--line-soft);padding-bottom:14px;margin-bottom:18px}.summary,.callout{background:#f8fafc;border:1px solid var(--line);border-radius:12px;padding:16px;margin:20px 0}.callout{background:var(--warn-bg);border-color:var(--warn-line)}
.table,.compare-table-wrap{overflow:auto;border:1px solid var(--line);border-radius:10px;margin:18px 0;background:#fff}.table table,.compare-table{border-collapse:collapse;width:100%}.table th,.table td,.compare-table th,.compare-table td{padding:11px 13px;border-bottom:1px solid var(--line-soft);text-align:left;vertical-align:top}.table th,.compare-table th{background:#f6f8fb;color:#344054;font-size:.92rem}.table tr:last-child td,.compare-table tr:last-child td{border-bottom:0}
code,kbd{background:var(--code);border:1px solid #e0e6ee;border-radius:5px;padding:.12em .3em}blockquote{border-left:4px solid #c7d5e4;padding-left:16px;color:#4b5563;margin-left:0}.footer{margin-top:52px;background:#fff;border-top:1px solid var(--line);padding:28px 0;color:var(--muted);font-size:.94rem}.footer a{color:#475467}.breadcrumbs{color:var(--muted);font-size:.9rem;margin-bottom:12px}.breadcrumbs a{color:#526476;text-decoration:none}.main-title{font-size:clamp(2rem,4vw,3.2rem);font-weight:800;letter-spacing:-.04em;line-height:1.1}.for-line{display:none}.hero-meta{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}.code-list{padding-left:1.2rem}.grid.three{grid-template-columns:repeat(3,minmax(0,1fr))}
@media(max-width:900px){.hero-grid,.layout,.grid,.grid.two,.grid.three,.card-grid,.directory,.callout-row{grid-template-columns:1fr}.side{position:static}.links{display:none}.hero{padding-top:30px}.article{max-width:none}}


/* Origins / history pages */
.timeline{position:relative;margin:22px 0;padding-left:22px;border-left:3px solid var(--line)}
.timeline-item{background:#fff;border:1px solid var(--line-soft);border-radius:10px;padding:14px 16px;margin:0 0 14px;box-shadow:0 1px 2px rgba(15,23,42,.025)}
.timeline-item strong{display:block;color:#1f3f5f;margin-bottom:2px}.fact-strip{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:18px 0}.fact{background:#f8fafc;border:1px solid var(--line);border-radius:10px;padding:14px}.fact b{display:block;color:#243b53}.formula{background:#f8fafc;border:1px solid var(--line);border-radius:10px;padding:14px;font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;overflow:auto}.source-list li{margin:.45em 0}.article .origin-note{background:#f7fbff;border:1px solid #d8e7f5;border-radius:12px;padding:15px;margin:18px 0}
@media(max-width:900px){.fact-strip{grid-template-columns:1fr}}