:root {
  --ink: #18212b;
  --ink-soft: #4f5b67;
  --ink-faint: #6d7884;
  --bg: #f5f7f9;
  --surface: #ffffff;
  --line: #e2e7ec;
  --line-strong: #cbd4dc;
  --accent: #c65a20;
  --accent-ink: #ffffff;
  --tint: #f5f7f9;
  --shadow: 0 5px 20px rgba(24, 33, 43, 0.045);
  --radius: 14px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #e8edf2;
    --ink-soft: #b3bec9;
    --ink-faint: #8d99a5;
    --bg: #131a21;
    --surface: #1b242d;
    --line: #2b3742;
    --line-strong: #3a4854;
    --accent: #e3762f;
    --accent-ink: #14191f;
    --tint: #222d37;
    --shadow: 0 5px 20px rgba(0, 0, 0, 0.25);
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
}

.wrap { max-width: 880px; margin: 0 auto; padding: 0 16px; }

/* ---------- masthead ---------- */

.masthead { border-bottom: 1px solid var(--line); background: var(--surface); }
.masthead .wrap { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; padding: 14px 16px; }
.brand { font-weight: 800; letter-spacing: -0.01em; color: var(--ink); text-decoration: none; font-size: 17px; }
.brand span { color: var(--accent); }

.sitenav { margin-left: auto; }
.sitenav ul { list-style: none; display: flex; gap: 16px; margin: 0; padding: 0; flex-wrap: wrap; }
.sitenav a { color: var(--ink-soft); text-decoration: none; font-size: 14px; font-weight: 600; }
.sitenav a:hover, .sitenav a:focus { color: var(--accent); text-decoration: underline; }

/* ---------- page head ---------- */

.crumbs { font-size: 13px; color: var(--ink-faint); padding: 18px 0 0; }
.crumbs a { color: var(--ink-faint); }
.crumbs ol { list-style: none; display: flex; gap: 6px; margin: 0; padding: 0; flex-wrap: wrap; }
.crumbs li:not(:last-child)::after { content: " /"; color: var(--line-strong); }

.pagehead { padding: 10px 0 4px; }
.eyebrow { font-weight: 800; letter-spacing: 0.14em; color: var(--accent); font-size: 11.5px; text-transform: uppercase; margin: 0 0 6px; }
h1 { font-size: clamp(28px, 5.2vw, 42px); line-height: 1.12; margin: 0 0 10px; letter-spacing: -0.02em; }
.lead { font-size: 17.5px; color: var(--ink-soft); margin: 0; max-width: 62ch; }

/* ---------- cards ---------- */

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  margin: 20px 0;
  box-shadow: var(--shadow);
}

/* ---------- calculator form ---------- */

.calc-top { display: flex; justify-content: flex-end; margin-bottom: 14px; }
.fields { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.field { display: flex; flex-direction: column; gap: 6px; min-width: 0; }
.field > label { font-weight: 650; font-size: 14.5px; }
.input-row { display: flex; align-items: stretch; }
.field input, .field select, .calc-top select {
  font: inherit;
  font-size: 16px;
  padding: 11px 12px;
  border: 1px solid var(--line-strong);
  border-radius: 9px;
  background: var(--surface);
  color: var(--ink);
  width: 100%;
  min-width: 0;
}
.input-row input { border-top-right-radius: 0; border-bottom-right-radius: 0; }
.input-row .unit {
  display: flex;
  align-items: center;
  padding: 0 11px;
  border: 1px solid var(--line-strong);
  border-left: 0;
  border-radius: 0 9px 9px 0;
  background: var(--tint);
  color: var(--ink-faint);
  font-size: 13px;
  white-space: nowrap;
}
.input-row .unit:empty { display: none; }
.input-row input:only-child { border-radius: 9px; }
.field input:focus, .field select:focus, .calc-top select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}
.hint { font-size: 12.5px; color: var(--ink-faint); margin: 0; line-height: 1.45; }

.calc-top label { font-size: 13px; font-weight: 650; color: var(--ink-faint); display: flex; align-items: center; gap: 8px; }
.calc-top select { width: auto; padding: 8px 10px; font-size: 14px; }

.primary {
  margin-top: 18px;
  background: var(--accent);
  color: var(--accent-ink);
  border: 0;
  border-radius: 10px;
  padding: 13px 22px;
  font: inherit;
  font-size: 16px;
  font-weight: 750;
  cursor: pointer;
}
.primary:hover { filter: brightness(1.07); }

/* ---------- results ---------- */

.results { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.result { background: var(--tint); border-radius: 11px; padding: 15px; min-width: 0; }
.result strong { display: block; font-size: clamp(20px, 3.4vw, 26px); line-height: 1.15; letter-spacing: -0.02em; overflow-wrap: break-word; }
.result span { display: block; font-size: 12.5px; color: var(--ink-faint); margin-top: 5px; }
.working { font-size: 13px; color: var(--ink-faint); margin: 14px 0 0; line-height: 1.55; }
.note { font-size: 13px; color: var(--ink-faint); margin: 12px 0 0; }

/* ---------- prose ---------- */

.prose { padding: 6px 0 0; }
.prose h2 { font-size: clamp(21px, 3.2vw, 26px); margin: 34px 0 10px; letter-spacing: -0.015em; }
.prose h2:first-child { margin-top: 20px; }
.prose p { color: var(--ink-soft); margin: 0 0 14px; max-width: 70ch; }
.prose ul { color: var(--ink-soft); max-width: 70ch; padding-left: 22px; }
.prose li { margin-bottom: 7px; }
.prose strong { color: var(--ink); }
.prose a { color: var(--accent); }
.prose abbr { text-decoration: underline dotted; cursor: help; }

.formula {
  background: var(--tint);
  border-left: 3px solid var(--accent);
  padding: 12px 14px;
  border-radius: 0 8px 8px 0;
  font-size: 15.5px;
  color: var(--ink) !important;
}

/* ---------- tables ---------- */

.table-scroll { overflow-x: auto; margin: 18px 0 24px; -webkit-overflow-scrolling: touch; }
table.ref {
  border-collapse: collapse;
  width: 100%;
  font-size: 14.5px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
table.ref caption {
  caption-side: top;
  text-align: left;
  font-size: 13px;
  font-weight: 700;
  color: var(--ink-faint);
  padding: 0 0 8px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
table.ref th, table.ref td { padding: 10px 13px; text-align: left; border-bottom: 1px solid var(--line); }
table.ref thead th { background: var(--tint); font-size: 13px; color: var(--ink); white-space: nowrap; }
table.ref tbody tr:last-child td { border-bottom: 0; }
table.ref td { color: var(--ink-soft); }
table.ref td:first-child { color: var(--ink); font-weight: 600; }

/* ---------- faq ---------- */

.faq h2 { margin-bottom: 4px; }
.faq details {
  border-bottom: 1px solid var(--line);
  padding: 14px 0;
}
.faq summary {
  font-weight: 680;
  cursor: pointer;
  font-size: 16px;
  list-style: none;
  display: flex;
  justify-content: space-between;
  gap: 14px;
  align-items: baseline;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; color: var(--accent); font-weight: 800; font-size: 19px; line-height: 1; }
.faq details[open] summary::after { content: "\2212"; }
.faq details p { color: var(--ink-soft); margin: 10px 0 0; max-width: 70ch; }

/* ---------- related & hub ---------- */

.related ul, .hub ul { list-style: none; margin: 0; padding: 0; }
.related ul { display: flex; flex-wrap: wrap; gap: 9px; }
.related a {
  display: inline-block;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  padding: 8px 14px;
  font-size: 14px;
  text-decoration: none;
  color: var(--ink-soft);
  background: var(--surface);
}
.related a:hover { border-color: var(--accent); color: var(--accent); }

.hub { margin: 26px 0; }
.hub h2 { font-size: 15px; text-transform: uppercase; letter-spacing: 0.08em; color: var(--ink-faint); margin: 0 0 12px; }
.hub ul { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; }
.hub li a {
  display: block;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 11px;
  padding: 15px 16px;
  text-decoration: none;
  height: 100%;
}
.hub li a:hover { border-color: var(--accent); }
.hub li strong { display: block; color: var(--ink); font-size: 16px; margin-bottom: 3px; }
.hub li span { display: block; color: var(--ink-faint); font-size: 13.5px; line-height: 1.45; }

/* ---------- ads ---------- */

.adslot { margin: 26px 0; min-height: 90px; text-align: center; }

/* ---------- footer ---------- */

footer.sitefoot { border-top: 1px solid var(--line); margin-top: 44px; padding: 24px 0 36px; color: var(--ink-faint); font-size: 14px; }
footer.sitefoot .wrap { display: flex; gap: 16px; flex-wrap: wrap; align-items: center; }
footer.sitefoot a { color: var(--ink-faint); }
footer.sitefoot nav { margin-left: auto; display: flex; gap: 16px; flex-wrap: wrap; }
.disclaimer { font-size: 13px; color: var(--ink-faint); margin: 12px 0 0; max-width: 78ch; }

/* ---------- small screens ---------- */

@media (max-width: 620px) {
  .fields, .results { grid-template-columns: 1fr; }
  .sitenav { margin-left: 0; width: 100%; }
  .sitenav ul { gap: 12px; }
  footer.sitefoot nav { margin-left: 0; }
  .masthead .wrap { gap: 10px; }
}

.contact-block { background: var(--tint); border-radius: 10px; padding: 14px 16px; }
.prose .formula { font-variant-numeric: tabular-nums; }

/* Verdict tiles: a limit check has to read as pass or fail at a glance. */
.result.pass { background: #e7f5ea; box-shadow: inset 0 0 0 1px #9ed4ae; }
.result.pass strong { color: #1c6b34; }
.result.fail { background: #fdeceb; box-shadow: inset 0 0 0 1px #edaba6; }
.result.fail strong { color: #a12b1e; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .result.pass { background: #17301f; box-shadow: inset 0 0 0 1px #2f6b42; }
  :root:not([data-theme="light"]) .result.pass strong { color: #86dba1; }
  :root:not([data-theme="light"]) .result.fail { background: #331a18; box-shadow: inset 0 0 0 1px #7a3a33; }
  :root:not([data-theme="light"]) .result.fail strong { color: #f3968b; }
}
.result strong { overflow-wrap: anywhere; }

/* Direct-answer block: the question as a heading, the answer in the first
   sentence. Styled to read as the answer, not as more prose. */
.prose.answer { margin: 22px 0 8px; }
.prose.answer h2 { margin-top: 0; }
.prose.answer .answer-lead {
  font-size: 18px;
  line-height: 1.55;
  color: var(--ink);
  background: var(--tint);
  border-left: 3px solid var(--accent);
  padding: 14px 16px;
  border-radius: 0 10px 10px 0;
  max-width: none;
}
.prose.answer .answer-lead strong { color: var(--ink); }