:root{
  --bg:#f6f4ef;--surface:#fffdf8;--ink:#1d2420;--muted:#5d665f;--line:#e2ddd2;
  --accent:#2f6b4f;--accent-2:#c8a96a;--accent-ink:#ffffff;--accent-soft:#e6f0e9;
  --warn:#8a500f;--warn-soft:#fbf0dc;--radius:14px;
}
@media (prefers-color-scheme:dark){
  :root{
    --bg:#121614;--surface:#1a201d;--ink:#e9ece8;--muted:#a2aca5;--line:#2b332e;
    --accent:#6fbf94;--accent-2:#d8b97a;--accent-ink:#0d1a13;--accent-soft:#1f3329;
    --warn:#e8b06a;--warn-soft:#33281a;
  }
}
*{box-sizing:border-box}
[hidden]{display:none!important}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.65 Inter,system-ui,-apple-system,"Segoe UI",sans-serif;font-variant-numeric:tabular-nums}
h1,h2,h3{font-family:Fraunces,Georgia,serif;font-weight:600;line-height:1.15;letter-spacing:-.01em}
h1{font-size:clamp(2rem,5vw,3rem);margin:.2em 0 .3em}
h2{font-size:1.6rem;margin:2em 0 .5em}
h3{font-size:1.15rem;margin:1.5em 0 .4em}
a{color:var(--accent)}
.wrap{max-width:1040px;margin:0 auto;padding:0 16px}

header.site{border-bottom:1px solid var(--line);background:var(--surface)}
.bar{display:flex;align-items:center;justify-content:space-between;height:60px}
.brand{display:flex;gap:10px;align-items:center;font-family:Fraunces,Georgia,serif;font-weight:700;font-size:1.25rem;color:var(--ink);text-decoration:none}
.mark{width:22px;height:22px;border-radius:6px;background:linear-gradient(135deg,var(--accent) 52%,var(--accent-2) 52%)}
header nav{display:flex;gap:20px}
header nav a{color:var(--muted);text-decoration:none;font-weight:500}
header nav a:hover{color:var(--ink)}

.crumbs{font-size:.875rem;color:var(--muted);margin:28px 0 0}
.crumbs a{color:var(--muted)}
.lede{font-size:1.125rem;color:var(--muted);max-width:660px;margin:0 0 28px}

.tool{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:28px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:24px;margin-bottom:24px}
@media (max-width:760px){.tool{grid-template-columns:1fr;padding:18px;gap:20px}}
.tool-head{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;grid-column:1/-1}
.tool-head h2{margin:0;font-size:1.25rem}
.form{display:flex;flex-direction:column;gap:16px}
.field{display:flex;flex-direction:column;gap:6px}
.field>.label{font-weight:600;font-size:.9rem}
.field .hint{font-size:.8rem;color:var(--muted)}
.row{display:flex;align-items:center;gap:8px}
.row em{font-style:normal;color:var(--muted);font-size:.9rem;min-width:22px}
input[type=number],select{width:100%;min-width:0;font:inherit;padding:10px 12px;border:1px solid var(--line);border-radius:10px;background:var(--bg);color:var(--ink)}
input[type=number]:focus,select:focus{outline:2px solid var(--accent);outline-offset:1px}
.check{display:flex;gap:10px;align-items:flex-start;font-size:.95rem;cursor:pointer}
.check input{margin-top:5px;accent-color:var(--accent);width:16px;height:16px;flex:none}

.seg,.units{display:inline-flex;flex-wrap:wrap;gap:2px;border:1px solid var(--line);border-radius:999px;padding:3px;background:var(--bg);align-self:flex-start}
.seg label{position:relative}
.seg input{position:absolute;opacity:0;pointer-events:none}
.seg span,.units button{display:block;padding:6px 14px;border-radius:999px;font:500 .9rem Inter,system-ui,sans-serif;cursor:pointer;color:var(--muted);border:0;background:none}
.seg input:checked+span,.units button[aria-pressed=true]{background:var(--accent);color:var(--accent-ink)}
.seg input:focus-visible+span,.units button:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

.result{background:var(--accent-soft);border-radius:12px;padding:22px;align-self:start}
.result .empty{color:var(--muted);margin:0}
.kicker{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);font-weight:600}
.big{font-family:Fraunces,Georgia,serif;font-size:3rem;font-weight:600;line-height:1.05;margin:4px 0}
.big small{font:500 1rem Inter,system-ui,sans-serif;color:var(--muted);margin-left:6px}
.pill{display:inline-block;background:var(--surface);border:1px solid var(--line);border-radius:999px;padding:2px 10px;font-size:.85rem;font-weight:600}
table.t{width:100%;border-collapse:collapse;margin-top:16px;font-size:.95rem}
.t th,.t td{text-align:left;padding:8px 6px;border-bottom:1px solid var(--line)}
.t th{font-size:.8rem;color:var(--muted);font-weight:600}
.t .n{text-align:right}
.t tr.hl td{font-weight:700;color:var(--accent)}
.note{font-size:.875rem;color:var(--muted);margin:12px 0 0}
.warn{background:var(--warn-soft);color:var(--warn);border-radius:10px;padding:10px 12px;font-size:.9rem;margin-top:14px}
.result ul{margin:10px 0 0;padding-left:20px}
.result li{margin:6px 0}

.explain{max-width:720px}
.formula{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:.88rem;background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:12px 14px;overflow-x:auto;white-space:pre}
.explain table.t{background:var(--surface)}

.related{margin:56px 0 0}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:16px}
.card{display:block;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:20px;text-decoration:none;color:var(--ink);transition:border-color .15s,transform .15s}
.card:hover{border-color:var(--accent);transform:translateY(-2px)}
.card .num{font-family:Fraunces,Georgia,serif;color:var(--accent-2);font-weight:700}
.card h3{margin:.3em 0 .3em}
.card p{margin:0;color:var(--muted);font-size:.95rem}

.hero{padding:72px 0 48px}
.hero h1{font-size:clamp(2.6rem,8vw,4.6rem);max-width:11ch;margin:0 0 .25em}
.hero p{font-size:1.2rem;color:var(--muted);max-width:560px;margin:0 0 28px}
.btn{display:inline-block;background:var(--accent);color:var(--accent-ink);padding:12px 22px;border-radius:999px;text-decoration:none;font-weight:600}
.principles{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:28px}
.principles h3{margin-top:0}
.principles p{color:var(--muted);margin:0}
.soon{background:var(--surface);border:1px dashed var(--line);border-radius:var(--radius);padding:24px;margin-top:56px}
.soon h2{margin:0 0 .3em;font-size:1.3rem}
.soon p{margin:0;color:var(--muted)}

footer.site{border-top:1px solid var(--line);margin-top:72px;padding:32px 0;color:var(--muted);font-size:.9rem}
.fine{font-size:.82rem;max-width:720px}

/* Chinese pages: system CJK fonts (Google Fonts is unreliable in mainland China) */
html[lang^=zh] body{font-family:-apple-system,"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Noto Sans CJK SC",sans-serif}
html[lang^=zh] h1,html[lang^=zh] h2,html[lang^=zh] h3{font-family:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Noto Sans CJK SC",sans-serif;font-weight:700;letter-spacing:0}
html[lang^=zh] .big small,html[lang^=zh] .seg span,html[lang^=zh] .units button{font-family:inherit}
.legal{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;font-size:.82rem;margin-top:12px}.legal a{color:var(--muted);text-decoration:none}.legal a:hover{text-decoration:underline}