:root{
  --accent:#d9531e; --accent2:#0f9d6b; --text:#1a1f2e; --muted:#5b647a;
  --ring:#e3e7f0; --soft:#f7f8fb;
}
*{box-sizing:border-box}
body{margin:0;font-family:system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif;background:#fff;color:var(--text);line-height:1.5}
.ribbon{display:flex;flex-direction:column;align-items:center;gap:8px;padding:12px 18px;background:rgba(255,255,255,.92);backdrop-filter:blur(8px);border-bottom:1px solid var(--ring);position:sticky;top:0;z-index:10}
.brand{font-weight:700;letter-spacing:.3px}
.ribbon nav{display:flex;flex-wrap:wrap;justify-content:center;gap:18px}
.ribbon nav a{color:var(--muted);text-decoration:none;font-size:.92rem}
.ribbon nav a:hover{color:var(--accent)}
main{max-width:860px;margin:0 auto;padding:28px 16px 50px}
h1{font-size:1.7rem;margin:.2em 0 .25em}
.lede{color:var(--muted);font-size:1rem;max-width:64ch;margin:.3em 0 0}
.tool{background:var(--soft);border:1px solid var(--ring);border-radius:14px;padding:14px;margin:18px 0;box-shadow:0 8px 24px rgba(20,30,60,.06)}
.field{display:flex;flex-direction:column;gap:3px;margin:7px 0}
.field label{font-size:.82rem;font-weight:600;color:var(--muted)}
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:8px}
input,select{background:#fff;color:var(--text);border:1px solid var(--ring);border-radius:7px;padding:8px 9px;font-size:.95rem;width:100%}
input:focus,select:focus{outline:2px solid var(--accent);border-color:var(--accent)}
.combo{display:flex;gap:6px}
.combo input{flex:1}
.combo .unitsel{width:74px;flex:0 0 74px}
.results{margin-top:12px;border-top:1px solid var(--ring);padding-top:12px;display:grid;grid-template-columns:repeat(auto-fit,minmax(110px,1fr));gap:8px}
.stat{background:#fff;border:1px solid var(--ring);border-radius:10px;padding:11px;text-align:center}
.stat .big{display:block;font-size:1.3rem;font-weight:800;color:var(--accent2)}
.stat .lbl{font-size:.74rem;color:var(--muted)}
.adv-toggle{margin-top:14px;cursor:pointer;background:#fff;border:1px solid var(--accent);color:var(--accent);font-weight:700;border-radius:9px;padding:10px 14px;width:100%;font-size:.95rem}
.adv-toggle:hover{background:#fff3ee}
[hidden]{display:none !important}
.advanced{margin-top:12px;display:flex;flex-direction:column;gap:8px}
.adv-block{background:#fff;border:1px solid var(--ring);border-radius:10px;padding:12px}
.adv-head{display:flex;align-items:center;gap:9px;font-weight:700;font-size:.95rem;cursor:pointer;color:var(--text)}
.adv-head input{width:auto;flex:0 0 auto}
.hint{font-size:.8rem;color:var(--muted);margin:.4em 0 0}
.grade-wrap{background:var(--soft);border:1px solid var(--ring);border-radius:9px;padding:8px;margin:8px 0}
h2{margin-top:32px}h3{margin-top:18px;color:var(--accent);font-size:1.02rem}
table.ref{width:100%;border-collapse:collapse;margin:12px 0;font-size:.92rem}
table.ref th,table.ref td{border:1px solid var(--ring);padding:8px 10px;text-align:left}
table.ref th{background:var(--soft);font-weight:700}
table.ref tr:nth-child(even) td{background:#fafbfd}
code{background:var(--soft);padding:2px 6px;border-radius:6px;border:1px solid var(--ring);font-size:.92em}
footer{border-top:1px solid var(--ring);color:var(--muted);text-align:center;padding:20px;font-size:.86rem}
@media (max-width:520px){
  h1{font-size:1.45rem}
  .lede{font-size:.92rem}
  main{padding:20px 12px 40px}
  .tool{padding:11px}
  .grid{grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:7px}
  .field{margin:5px 0}
  .combo .unitsel{flex:0 0 66px;width:66px}
  .stat .big{font-size:1.15rem}
}