:root {
  --bg: #faf8f4;
  --surface: #ffffff;
  --ink: #1f2328;
  --muted: #5b6470;
  --line: #e4ded3;
  --accent: #c2410c;
  --accent-ink: #ffffff;
  --accent-soft: #fff1e8;
  --result: #0f5132;
  --result-bg: #e8f5ee;
  --radius: 10px;
  --max: 980px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #15171a; --surface: #1d2024; --ink: #e9e6e1; --muted: #a2a9b3;
    --line: #2e333a; --accent: #fb923c; --accent-ink: #1a1a1a; --accent-soft: #2a1e16;
    --result: #86efac; --result-bg: #13291d;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 17px/1.65 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
a { color: var(--accent); }
img { max-width: 100%; }
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 16px; }

/* header / footer */
.site-header { background: var(--surface); border-bottom: 1px solid var(--line); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding-top: 14px; padding-bottom: 14px; flex-wrap: wrap; }
.logo { font-weight: 800; font-size: 1.25rem; color: var(--ink); text-decoration: none; letter-spacing: -0.02em; }
.logo span { color: var(--accent); }
.site-header nav a { color: var(--muted); text-decoration: none; margin-left: 18px; font-size: 0.95rem; }
.site-header nav a:hover { color: var(--ink); }
.site-footer { border-top: 1px solid var(--line); margin-top: 64px; padding: 28px 0; color: var(--muted); font-size: 0.9rem; }
.site-footer a { color: var(--muted); margin-right: 16px; }

/* home */
.hero { padding: 48px 0 24px; }
.hero h1 { font-size: clamp(1.9rem, 5vw, 2.8rem); line-height: 1.15; margin: 0 0 12px; letter-spacing: -0.02em; }
.hero p { color: var(--muted); max-width: 640px; margin: 0; font-size: 1.1rem; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 16px; margin: 28px 0; }
.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 h2, .card h3, .prose .card h3 { margin: 0 0 6px; font-size: 1.15rem; }
.card p { margin: 0; color: var(--muted); font-size: 0.95rem; }
.card .tag { display: inline-block; font-size: 0.75rem; text-transform: uppercase; letter-spacing: .06em; color: var(--accent); font-weight: 700; margin-bottom: 8px; }

/* calculator page */
.breadcrumb { font-size: 0.85rem; color: var(--muted); margin: 24px 0 8px; }
.breadcrumb a { color: var(--muted); }
article h1 { font-size: clamp(1.7rem, 4.5vw, 2.4rem); line-height: 1.2; margin: 0 0 10px; letter-spacing: -0.02em; }
.lede { color: var(--muted); font-size: 1.08rem; margin: 0 0 24px; }
.calc { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; margin: 0 0 32px; }
.fields { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 14px 18px; }
.field label { display: block; font-weight: 600; font-size: 0.92rem; margin-bottom: 4px; }
.field small { display: block; color: var(--muted); font-size: 0.8rem; margin-top: 3px; }
.field input, .field select {
  width: 100%; padding: 10px 12px; font: inherit; color: var(--ink);
  background: var(--bg); border: 1px solid var(--line); border-radius: 8px;
}
.field input:focus, .field select:focus { outline: 2px solid var(--accent); outline-offset: 1px; border-color: transparent; }
.units { display: flex; gap: 8px; margin-bottom: 16px; }
.units button { font: inherit; font-size: .9rem; padding: 6px 14px; border-radius: 999px; border: 1px solid var(--line); background: var(--bg); color: var(--ink); cursor: pointer; }
.units button[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.result { margin-top: 20px; padding: 18px; border-radius: 8px; background: var(--result-bg); color: var(--result); }
.result .big { font-size: 1.7rem; font-weight: 800; line-height: 1.2; }
.result ul { margin: 8px 0 0; padding-left: 20px; }
.result .err { color: var(--accent); }

.prose h2 { font-size: 1.45rem; margin: 36px 0 10px; letter-spacing: -0.01em; }
.prose h3 { font-size: 1.15rem; margin: 24px 0 8px; }
.prose table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 0.95rem; display: block; overflow-x: auto; }
.prose th, .prose td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; }
.prose th { background: var(--accent-soft); }
.formula { background: var(--accent-soft); border-left: 4px solid var(--accent); padding: 12px 16px; border-radius: 6px; font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 0.92rem; overflow-x: auto; }
.faq dt { font-weight: 700; margin-top: 16px; }
.faq dd { margin: 4px 0 0; color: var(--ink); }
.related { margin-top: 40px; }
.ad-slot { margin: 28px 0; min-height: 0; }
.updated { color: var(--muted); font-size: 0.85rem; }

/* home search */
.search { margin: 8px 0 0; max-width: 520px; }
.search label { display: block; font-weight: 600; font-size: 0.92rem; margin-bottom: 4px; }
.search input { width: 100%; padding: 12px 14px; font: inherit; color: var(--ink); background: var(--surface); border: 1px solid var(--line); border-radius: 8px; }
.search input:focus { outline: 2px solid var(--accent); outline-offset: 1px; border-color: transparent; }
.search small { display: block; color: var(--muted); font-size: 0.8rem; margin-top: 4px; }
[hidden] { display: none !important; }