:root {
  --bg: #f7f7f4;
  --surface: #ffffff;
  --surface-2: #f0f0eb;
  --text: #1c1d1f;
  --muted: #5b5f66;
  --border: #e2e2dc;
  --accent: #c2410c;
  --accent-ink: #ffffff;
  --accent-soft: #fff1e8;
  --focus: #2563eb;
  --danger: #b91c1c;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 4px 16px rgba(0,0,0,.05);
  --max: 1120px;
  --font: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #141516;
    --surface: #1c1d1f;
    --surface-2: #26272a;
    --text: #ececea;
    --muted: #a3a6ab;
    --border: #33353a;
    --accent: #fb923c;
    --accent-ink: #1c1d1f;
    --accent-soft: #2d2018;
    --focus: #60a5fa;
    --danger: #f87171;
    --shadow: none;
  }
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.6 var(--font);
}
a { color: var(--accent); text-underline-offset: 2px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }
img, svg { max-width: 100%; height: auto; }
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 16px; }

/* Header / footer */
.site-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 60px; }
.logo { display: flex; align-items: center; gap: 10px; color: var(--text); text-decoration: none; font-weight: 700; font-size: 1.15rem; letter-spacing: -.01em; }
.logo-mark { width: 30px; height: 30px; border-radius: 8px; background: var(--accent); color: var(--accent-ink); display: grid; place-items: center; font-size: 15px; font-weight: 800; }
.site-nav { display: flex; gap: 18px; font-size: .95rem; }
.site-nav a { color: var(--muted); text-decoration: none; }
.site-nav a:hover { color: var(--text); }
.site-footer { margin-top: 64px; border-top: 1px solid var(--border); background: var(--surface); color: var(--muted); font-size: .9rem; }
.site-footer .wrap { padding-top: 28px; padding-bottom: 28px; display: flex; flex-wrap: wrap; gap: 12px 28px; justify-content: space-between; }
.site-footer nav { display: flex; flex-wrap: wrap; gap: 8px 18px; }
.site-footer a { color: var(--muted); }

/* Typography */
h1 { font-size: clamp(1.7rem, 4vw, 2.3rem); line-height: 1.2; letter-spacing: -.02em; margin: 8px 0 8px; }
h2 { font-size: 1.4rem; line-height: 1.3; margin: 36px 0 10px; letter-spacing: -.01em; }
h3 { font-size: 1.12rem; margin: 24px 0 8px; }
.lede { color: var(--muted); font-size: 1.08rem; margin: 0 0 20px; max-width: 70ch; }
.crumbs { font-size: .88rem; color: var(--muted); margin-top: 20px; }
.crumbs a { color: var(--muted); }

/* Calculator */
.calc { display: grid; grid-template-columns: minmax(0, 1.2fr) minmax(0, 1fr); gap: 20px; align-items: start; }
@media (max-width: 820px) { .calc { grid-template-columns: 1fr; } }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); padding: 20px; }
.calc-top { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 14px; flex-wrap: wrap; }
.calc-top h2 { margin: 0; font-size: 1.05rem; }
.seg { display: inline-flex; background: var(--surface-2); border-radius: 999px; padding: 3px; }
.seg button { border: 0; background: transparent; color: var(--muted); font: inherit; font-size: .88rem; padding: 5px 14px; border-radius: 999px; cursor: pointer; }
.seg button[aria-pressed="true"] { background: var(--surface); color: var(--text); box-shadow: 0 1px 2px rgba(0,0,0,.12); font-weight: 600; }
.fields { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px 16px; }
@media (max-width: 480px) { .fields { grid-template-columns: 1fr; } }
.field { display: flex; flex-direction: column; gap: 5px; }
.field.wide { grid-column: 1 / -1; }
.field[hidden] { display: none; }
.field label { font-size: .9rem; font-weight: 600; }
.field .hint { font-size: .8rem; color: var(--muted); }
.input { display: flex; align-items: stretch; border: 1px solid var(--border); border-radius: 8px; background: var(--surface); overflow: hidden; }
.input:focus-within { border-color: var(--focus); box-shadow: 0 0 0 3px color-mix(in srgb, var(--focus) 20%, transparent); }
.input input, .input select { flex: 1; min-width: 0; border: 0; background: transparent; color: var(--text); font: inherit; padding: 9px 11px; outline: none; }
.input select { cursor: pointer; }
.input .u { display: flex; align-items: center; padding: 0 11px; background: var(--surface-2); color: var(--muted); font-size: .85rem; white-space: nowrap; }
.input .u:empty { display: none; }
input[aria-invalid="true"] { color: var(--danger); }
.input:has(input[aria-invalid="true"]) { border-color: var(--danger); }
.tip { font-size: .82rem; color: var(--muted); margin: 14px 0 0; }
.tip[hidden] { display: none; }
.tip code { background: var(--surface-2); padding: 1px 5px; border-radius: 4px; font-size: .95em; }
.calc-bar { display: none; }
@media (max-width: 820px) {
  .calc-bar:not([hidden]) {
    position: sticky; top: 0; z-index: 5; display: flex; align-items: center; justify-content: space-between; gap: 10px;
    margin: 0 -20px 14px; padding: 10px 20px;
    background: var(--accent-soft); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border);
    color: var(--text); text-decoration: none; font-size: .95rem; font-variant-numeric: tabular-nums;
  }
  .calc-bar.off { visibility: hidden; }
  .calc-bar em { font-style: normal; color: var(--accent); font-size: .85rem; white-space: nowrap; }
}
.calc-actions { display: flex; gap: 10px; margin-top: 16px; flex-wrap: wrap; }
.btn { border: 1px solid var(--border); background: var(--surface); color: var(--text); font: inherit; font-size: .9rem; padding: 7px 14px; border-radius: 8px; cursor: pointer; }
.btn:hover { background: var(--surface-2); }
.results { position: sticky; top: 16px; background: var(--accent-soft); border-color: color-mix(in srgb, var(--accent) 25%, var(--border)); }
.results h2 { margin: 0 0 12px; font-size: 1.05rem; }
.res-primary { padding: 4px 0 14px; }
.res-primary + .res-primary { border-top: 1px dashed var(--border); padding-top: 14px; }
.res-label { font-size: .9rem; color: var(--muted); }
.res-value { font-size: clamp(1.8rem, 5vw, 2.4rem); font-weight: 750; letter-spacing: -.02em; line-height: 1.15; font-variant-numeric: tabular-nums; }
.res-value span { font-size: .5em; font-weight: 600; color: var(--muted); letter-spacing: 0; }
.res-note { font-size: .82rem; color: var(--muted); margin-top: 4px; }
.res-list { margin: 0; border-top: 1px solid var(--border); }
.res-list > div { display: flex; justify-content: space-between; gap: 12px; padding: 8px 0; border-bottom: 1px solid var(--border); }
.res-list dt { color: var(--muted); font-size: .92rem; }
.res-list dd { margin: 0; font-weight: 650; text-align: right; font-variant-numeric: tabular-nums; }
.res-msg { color: var(--muted); margin: 0; }
.disclaimer { font-size: .8rem; color: var(--muted); margin: 14px 0 0; }

/* Article */
.page-grid { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 40px; margin-top: 8px; }
@media (max-width: 960px) { .page-grid { grid-template-columns: 1fr; } }
.article { max-width: 72ch; }
.article p, .article li { color: var(--text); }
.article ul, .article ol { padding-left: 1.3em; }
.article table { width: 100%; border-collapse: collapse; margin: 12px 0 20px; font-size: .93rem; display: block; overflow-x: auto; }
.article th, .article td { border-bottom: 1px solid var(--border); padding: 8px 10px; text-align: left; white-space: nowrap; }
.article th { background: var(--surface-2); font-weight: 650; }
.formula { background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--accent); border-radius: 8px; padding: 12px 16px; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .92rem; overflow-x: auto; }
.callout { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 18px; margin: 18px 0; }
.faq details { border-bottom: 1px solid var(--border); padding: 12px 0; }
.faq summary { cursor: pointer; font-weight: 650; }
.faq details p { margin: 8px 0 0; }
.meta { font-size: .85rem; color: var(--muted); margin-top: 28px; }
.side h2 { font-size: 1rem; margin: 0 0 10px; }
.side ul { list-style: none; margin: 0; padding: 0; }
.side li a { display: block; padding: 8px 0; border-bottom: 1px solid var(--border); text-decoration: none; color: var(--text); }
.side li a:hover { color: var(--accent); }
.side .sticky { position: sticky; top: 16px; display: grid; gap: 24px; }

/* Ads: reserve space to avoid layout shift once ads are enabled */
.ad { margin: 24px 0; min-height: 100px; text-align: center; }
.ad-side { min-height: 250px; }

/* Home */
.hero { padding: 40px 0 8px; }
.hero h1 { font-size: clamp(2rem, 5vw, 2.8rem); max-width: 22ch; }
.search { margin: 18px 0 8px; max-width: 520px; }
.search input { width: 100%; font: inherit; padding: 12px 14px; border-radius: 10px; border: 1px solid var(--border); background: var(--surface); color: var(--text); }
.cat h2 { font-size: 1.15rem; margin: 36px 0 12px; }
.tiles { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 14px; }
.tile { display: block; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px 18px; text-decoration: none; color: var(--text); transition: border-color .15s, transform .15s; }
.tile:hover { border-color: var(--accent); transform: translateY(-1px); }
.tile strong { display: block; font-size: 1rem; margin-bottom: 4px; }
.tile span { color: var(--muted); font-size: .9rem; line-height: 1.45; }
.tile[hidden] { display: none; }
.prose { max-width: 72ch; }

@media print {
  .site-header, .site-footer, .ad, .side, .calc-actions, .seg { display: none !important; }
  .calc { grid-template-columns: 1fr 1fr; }
  body { background: #fff; }
}