/* Layout: one narrow column, tool cards in a 2-col grid that stacks on phones. System fonts only, for speed. */
:root{
  --bg:#f5f7f4;--surface:#ffffff;--ink:#16211c;--muted:#5a6660;--line:#dde2dc;
  --accent:#0d6a4c;--accent-soft:#e2f0e8;--bad:#a23b2c;
  --sans:system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  --mono:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#0f1513;--surface:#161e1b;--ink:#e6ede9;--muted:#9ba9a2;--line:#29342f;
  --accent:#5fcf9f;--accent-soft:#1a2f26;--bad:#f08a78;color-scheme:dark}}
:root[data-theme="dark"]{
  --bg:#0f1513;--surface:#161e1b;--ink:#e6ede9;--muted:#9ba9a2;--line:#29342f;
  --accent:#5fcf9f;--accent-soft:#1a2f26;--bad:#f08a78;color-scheme:dark}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.55 var(--sans)}
a{color:var(--accent)}
.wrap{max-width:960px;margin:0 auto;padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
header.top{border-bottom:1px solid var(--line);background:var(--surface)}
header.top .wrap{display:flex;align-items:center;justify-content:space-between;gap:12px;padding-block:12px;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:8px;font-weight:700;font-size:1.1rem;color:var(--ink);text-decoration:none;letter-spacing:-.01em}
.brand b{display:inline-grid;place-items:center;width:28px;height:28px;border-radius:7px;background:var(--accent);color:var(--surface);font-size:.95rem}
nav.lang{display:flex;gap:4px;flex-wrap:wrap}
nav.lang a{font-size:.8rem;font-weight:600;letter-spacing:.06em;text-decoration:none;color:var(--muted);padding:5px 8px;border-radius:6px}
nav.lang a[aria-current="page"]{background:var(--accent-soft);color:var(--accent)}
nav.lang a:hover{color:var(--ink)}
main{padding-block:28px 48px}
h1{font-size:clamp(1.7rem,4.5vw,2.3rem);line-height:1.15;margin:0 0 8px;letter-spacing:-.02em;text-wrap:balance}
.lead{color:var(--muted);max-width:62ch;margin:0 0 24px}
.grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}
@media (max-width:680px){.grid{grid-template-columns:minmax(0,1fr)}}
.calc{background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:16px;display:flex;flex-direction:column;gap:10px;min-width:0}
.calc h2{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);margin:0;font-weight:700}
.q{display:flex;flex-wrap:wrap;align-items:center;gap:6px;font-size:1.02rem}
.q input{width:7.5ch;font:600 1.05rem var(--sans);color:var(--ink);background:var(--bg);border:1px solid var(--line);border-radius:7px;padding:6px 8px;text-align:right;font-variant-numeric:tabular-nums}
.q input:focus{outline:2px solid var(--accent);outline-offset:1px;border-color:transparent}
.q input[aria-invalid="true"]{border-color:var(--bad)}
.res{display:flex;align-items:baseline;gap:8px;flex-wrap:wrap;border-top:1px dashed var(--line);padding-top:10px}
.out{font-size:1.65rem;font-weight:700;color:var(--accent);font-variant-numeric:tabular-nums;letter-spacing:-.01em;overflow-wrap:anywhere}
.out.err{font-size:.95rem;color:var(--bad);font-weight:600}
.tag{font-size:.78rem;font-weight:600;color:var(--muted)}
.steps{font:.85rem var(--mono);color:var(--muted);overflow-wrap:anywhere}
section.content{margin-top:40px;max-width:68ch}
section.content h2{font-size:1.3rem;margin:32px 0 10px;letter-spacing:-.01em}
.formulas{list-style:none;padding:0;margin:0;display:grid;gap:8px}
.formulas li{background:var(--surface);border:1px solid var(--line);border-radius:8px;padding:10px 12px;font-family:var(--mono);font-size:.9rem}
.tablebox{overflow-x:auto;border:1px solid var(--line);border-radius:8px;background:var(--surface)}
table{border-collapse:collapse;width:100%;font-variant-numeric:tabular-nums;font-size:.92rem}
th,td{padding:7px 10px;text-align:right;border-bottom:1px solid var(--line);white-space:nowrap}
th{color:var(--muted);font-weight:600;font-size:.8rem}
tbody th{color:var(--accent);font-size:.92rem}
tr:last-child td,tr:last-child th{border-bottom:0}
details{border-bottom:1px solid var(--line);padding:10px 0}
summary{cursor:pointer;font-weight:600}
summary:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
details p{margin:8px 0 0;color:var(--muted)}
footer{border-top:1px solid var(--line);color:var(--muted);font-size:.85rem}
footer .wrap{padding-block:20px;display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}
.picker{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:12px;margin-top:20px}
.picker a{display:flex;flex-direction:column;gap:2px;background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:14px 16px;text-decoration:none;color:var(--ink)}
.picker a:hover{border-color:var(--accent)}
.picker span{color:var(--muted);font-size:.85rem}
@media (prefers-reduced-motion:no-preference){.out{transition:color .15s}}

footer .flinks{display:flex;gap:16px;flex-wrap:wrap}footer .flinks a{color:inherit}