:root {
  --bg: #0b0e14;
  --bg-2: #121722;
  --card: #161c28;
  --line: #232c3d;
  --txt: #e6edf6;
  --muted: #97a3b6;
  --faint: #5f6b80;
  --accent: #57c7ff;
  --accent-2: #7df0c2;
  --warn: #ffb454;
  --err: #ff6b6b;
  --radius: 14px;
  --maxw: 980px;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--txt);
  font: 16px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.topbar {
  position: sticky; top: 0; z-index: 10;
  background: rgba(11,14,20,.85); backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 14px 20px;
  display: flex; align-items: center; gap: 12px;
}
.topbar .logo { font-weight: 800; font-size: 18px; letter-spacing: -.02em; }
.topbar .logo em { color: var(--accent); font-style: normal; }
.topbar .sub { color: var(--faint); font-size: 13px; }

main { max-width: var(--maxw); margin: 0 auto; padding: 24px 20px 80px; }

.hero { padding: 34px 0 18px; }
.hero h1 { font-size: clamp(34px, 6vw, 56px); margin: 0 0 10px; letter-spacing: -.03em; }
.hero h1 em { color: var(--accent); font-style: normal; }
.hero .lead { color: var(--muted); font-size: 18px; max-width: 640px; margin: 0 0 24px; }

.searchbox input {
  width: 100%; padding: 16px 18px; font-size: 17px;
  background: var(--bg-2); border: 1px solid var(--line); border-radius: var(--radius);
  color: var(--txt); outline: none;
}
.searchbox input:focus { border-color: var(--accent); }

.cat { margin: 34px 0 0; }
.cat h2 { font-size: 20px; display: flex; align-items: center; gap: 10px; margin: 0 0 14px; }
.cat h2 .emoji { font-size: 22px; }
.cat h2 .count {
  margin-left: auto; font-size: 13px; color: var(--faint);
  background: var(--bg-2); border: 1px solid var(--line); border-radius: 20px; padding: 2px 10px;
}
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 12px; }
.card {
  display: block; background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 16px; color: var(--txt);
  transition: border-color .15s, transform .1s;
}
.card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-2px); }
.card.external { border-style: dashed; }
.card.external:hover { border-color: var(--accent-2); }
.card h3 { margin: 0 0 6px; font-size: 16px; }
.card p { margin: 0; color: var(--muted); font-size: 13.5px; line-height: 1.45; }
.empty { color: var(--faint); padding: 40px 0; text-align: center; }

.crumbs { margin: 6px 0 16px; font-size: 14px; color: var(--faint); }
.crumbs .crumb-cat { color: var(--muted); }

.calc-head h1 { font-size: clamp(26px, 4vw, 38px); margin: 0 0 4px; letter-spacing: -.02em; }
.calc-head .en { color: var(--faint); margin: 0 0 8px; font-size: 14px; }
.calc-head .desc { color: var(--muted); margin: 0 0 20px; font-size: 17px; }

.calc-form {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px; display: grid; gap: 16px;
}
.field { display: grid; gap: 6px; }
.field label { font-size: 14px; color: var(--muted); }
.in-wrap { display: flex; align-items: center; gap: 8px; }
.in-wrap input, .in-wrap select {
  flex: 1; padding: 11px 13px; font-size: 16px;
  background: var(--bg); border: 1px solid var(--line); border-radius: 10px; color: var(--txt); outline: none;
}
.in-wrap input:focus, .in-wrap select:focus { border-color: var(--accent); }
.in-wrap .unit { color: var(--faint); font-size: 14px; min-width: 38px; }
.field .hint { color: var(--faint); font-size: 12.5px; }

.calc-out { margin: 18px 0 0; }
.outputs { display: grid; gap: 10px; }
.result {
  display: flex; align-items: baseline; justify-content: space-between; gap: 16px;
  background: var(--bg-2); border: 1px solid var(--line); border-radius: 12px; padding: 14px 18px;
}
.result.primary { border-color: var(--accent-2); background: linear-gradient(180deg, rgba(125,240,194,.08), rgba(125,240,194,.02)); }
.result .r-label { color: var(--muted); font-size: 15px; }
.result .r-val { font-size: 22px; font-weight: 700; font-variant-numeric: tabular-nums; }
.result.primary .r-val { color: var(--accent-2); }
.result .r-unit { font-size: 14px; color: var(--faint); font-weight: 500; }

.formula {
  margin: 14px 0; padding: 12px 16px; background: var(--bg); border-left: 3px solid var(--accent);
  border-radius: 0 8px 8px 0; font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 15px; color: var(--accent-2);
  overflow-x: auto;
}
.steps-d { margin: 12px 0; background: var(--bg-2); border: 1px solid var(--line); border-radius: 10px; padding: 8px 16px; }
.steps-d summary { cursor: pointer; color: var(--muted); font-size: 14px; padding: 6px 0; }
.steps { margin: 8px 0; padding-left: 20px; }
.steps li { margin: 5px 0; font-family: ui-monospace, monospace; font-size: 14px; color: var(--txt); }
.note { color: var(--muted); font-size: 14px; background: var(--bg-2); border: 1px solid var(--line); border-radius: 10px; padding: 12px 16px; }
.err { color: var(--err); background: rgba(255,107,107,.08); border: 1px solid rgba(255,107,107,.3); border-radius: 10px; padding: 12px 16px; }

.explain { margin: 40px 0 0; }
.explain h2 { font-size: 20px; margin: 0 0 12px; }
.explain p { color: var(--muted); }
.explain code { background: var(--bg-2); padding: 2px 6px; border-radius: 5px; font-size: 14px; }

/* статья «теория за расчётом» */
.article { margin: 40px 0 0; max-width: 760px; line-height: 1.7; }
.article h2 { font-size: 24px; margin: 36px 0 12px; letter-spacing: -.01em; }
.article h2:first-child { margin-top: 0; }
.article h3 { font-size: 18px; margin: 26px 0 8px; color: var(--accent-2); }
.article p { color: #c4cedd; margin: 0 0 14px; }
.article ul, .article ol { color: #c4cedd; margin: 0 0 14px; padding-left: 24px; }
.article li { margin: 6px 0; }
.article code { background: var(--bg-2); padding: 2px 6px; border-radius: 5px; font-size: 14.5px; color: var(--accent-2); }
.article b, .article strong { color: var(--txt); }
.article .eq {
  display: block; margin: 16px 0; padding: 14px 18px; background: var(--bg);
  border-left: 3px solid var(--accent); border-radius: 0 8px 8px 0;
  font-family: "SF Mono", ui-monospace, Menlo, monospace; font-size: 16px; color: var(--accent-2); overflow-x: auto;
}
.article .example, .article .ex {
  margin: 18px 0; padding: 16px 18px; background: var(--bg-2);
  border: 1px solid var(--line); border-radius: 12px;
}
.article .example h4, .article .ex h4 { margin: 0 0 8px; font-size: 15px; color: var(--accent); }
.article .mistakes, .article .warn {
  margin: 18px 0; padding: 14px 18px; background: rgba(255,180,84,.07);
  border: 1px solid rgba(255,180,84,.3); border-radius: 12px;
}
.article .mistakes h4 { margin: 0 0 8px; font-size: 15px; color: var(--warn); }
.article table { border-collapse: collapse; margin: 14px 0; width: 100%; font-size: 14.5px; }
.article th, .article td { border: 1px solid var(--line); padding: 8px 12px; text-align: left; }
.article th { background: var(--bg-2); color: var(--muted); }

.cta { margin: 44px 0 0; }
.cta-inner {
  background: linear-gradient(135deg, rgba(87,199,255,.10), rgba(125,240,194,.06));
  border: 1px solid var(--accent); border-radius: 18px; padding: 28px;
}
.cta-inner h2 { margin: 0 0 8px; font-size: 22px; }
.cta-inner p { color: var(--muted); margin: 0 0 18px; max-width: 620px; }
.cta-btns { display: flex; gap: 10px; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 8px; padding: 11px 20px;
  border-radius: 10px; border: 1px solid var(--line); background: var(--bg-2);
  color: var(--txt); font-weight: 600; font-size: 15px;
}
.btn:hover { text-decoration: none; border-color: var(--accent); }
.btn.primary { background: var(--accent); color: #04202e; border-color: var(--accent); }

.related { margin: 44px 0 0; }
.related h2 { font-size: 18px; margin: 0 0 12px; }

/* embed-режим (?embed=<id>) — для вставки в <iframe> на чужом сайте */
body.embed .topbar, body.embed .footer { display: none; }
body.embed main { padding: 16px; max-width: 560px; }
body.embed .calc-head h1 { font-size: 22px; }
body.embed .calc-head .en { display: none; }
.embed-credit { margin: 16px 0 0; font-size: 12px; text-align: right; }
.embed-credit a { color: var(--faint); }

.footer { border-top: 1px solid var(--line); margin-top: 60px; }
.footer-inner { max-width: var(--maxw); margin: 0 auto; padding: 28px 20px; color: var(--faint); font-size: 13.5px; }
.footer-inner a { color: var(--muted); }

@media (max-width: 560px) {
  .result { flex-direction: column; align-items: flex-start; gap: 4px; }
}