:root {
  --accent: #0f766e;
  --accent-dark: #115e59;
  --accent-soft: #f0fdfa;
  --text: #1e293b;
  --muted: #475569;
  --line: #64748b;
  --line-soft: #e2e8f0;
  --bg: #f8fafc;
  --card: #ffffff;
  --error: #b91c1c;
  --radius: 10px;
}

*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }
@media (prefers-reduced-motion: no-preference) { html { scroll-behavior: smooth; } }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: 1rem;
  line-height: 1.55;
  color: var(--text);
  background: var(--bg);
}

.wrap { max-width: 1000px; margin: 0 auto; padding: 1rem; }

h1 { font-size: clamp(1.6rem, 4.5vw, 2.25rem); line-height: 1.2; margin: 0.75rem 0 0.5rem; color: #0f172a; }
h2 { font-size: 1.35rem; line-height: 1.3; margin: 2rem 0 0.6rem; color: #0f172a; }
h3 { font-size: 1.1rem; margin: 1.4rem 0 0.4rem; color: #0f172a; }
h4 { font-size: 0.95rem; margin: 1rem 0 0.35rem; color: #0f172a; }
p { margin: 0 0 0.8rem; }
a { color: var(--accent-dark); }
.lede { color: var(--muted); max-width: 60ch; }

:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }

.skip-link {
  position: absolute; left: 0.5rem; top: -3rem; z-index: 10;
  background: var(--accent); color: #fff; padding: 0.5rem 0.9rem; border-radius: 6px;
}
.skip-link:focus { top: 0.5rem; }

/* ---------- tool layout ---------- */
.tool { display: grid; gap: 1rem; margin-top: 1rem; }
@media (min-width: 860px) {
  .tool { grid-template-columns: minmax(0, 5fr) minmax(0, 6fr); align-items: start; }
}

.tool-form, .results {
  background: var(--card);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  padding: 1rem;
}

.group { border: 0; padding: 0; margin: 0 0 1.25rem; min-width: 0; }
.group > legend { font-weight: 700; font-size: 1.05rem; padding: 0; margin-bottom: 0.4rem; color: #0f172a; }
.subgroup { border: 0; padding: 0; margin: 0.75rem 0; min-width: 0; }
.subgroup > legend { font-weight: 600; padding: 0; margin-bottom: 0.3rem; }

.field { margin-bottom: 0.6rem; min-width: 0; }
.field label { display: block; font-weight: 600; margin-bottom: 0.2rem; }
.u-label { font-weight: 400; color: var(--muted); }
.pair { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; }

input[type="number"] {
  width: 100%;
  font: inherit;
  padding: 0.5rem 0.6rem;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #fff;
  color: var(--text);
}
input[aria-invalid="true"] { border: 2px solid var(--error); }

.hint { font-size: 0.875rem; color: var(--muted); margin: 0.2rem 0 0.5rem; }
.error { font-size: 0.875rem; color: var(--error); font-weight: 600; margin: 0.25rem 0 0; }
.error:empty { display: none; }
.error:not(:empty)::before { content: "⚠ "; content: "⚠ " / ""; }

[data-units="in"] .only-cm, [data-units="cm"] .only-in { display: none; }

/* segmented units switch */
.segmented { display: inline-flex; border: 1px solid var(--accent); border-radius: 8px; overflow: hidden; }
.segmented input { position: absolute; opacity: 0; width: 1px; height: 1px; }
.segmented label { padding: 0.45rem 1rem; cursor: pointer; font-weight: 600; color: var(--accent-dark); background: #fff; }
.segmented label + input + label { border-left: 1px solid var(--accent); }
.segmented input:checked + label { background: var(--accent); color: #fff; }
.segmented input:checked + label::before { content: "✓ "; content: "✓ " / ""; }
.segmented input:focus-visible + label { box-shadow: inset 0 0 0 3px #fff, inset 0 0 0 5px #0f172a; }

/* radio choices */
.choice { display: grid; grid-template-columns: auto 1fr; column-gap: 0.5rem; margin-bottom: 0.35rem; }
.choice input { margin: 0.3rem 0 0; width: 1.1rem; height: 1.1rem; accent-color: var(--accent); }
.choice label { font-weight: 600; cursor: pointer; }
.choice .hint { grid-column: 2; margin: 0 0 0.3rem; }

/* borders */
.border-list { list-style: none; margin: 0; padding: 0; }
.border-row { display: flex; align-items: flex-end; gap: 0.5rem; }
.border-row .field { flex: 1; }
.border-row .btn-link { margin-bottom: 0.7rem; }

/* buttons */
.btn {
  font: inherit; font-weight: 600; cursor: pointer;
  border-radius: 6px; padding: 0.55rem 1rem; border: 1px solid var(--accent);
}
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-dark); }
.btn-secondary { background: #fff; color: var(--accent-dark); }
.btn-secondary:hover { background: var(--accent-soft); }
.btn-link { background: none; border: 0; padding: 0.4rem 0.2rem; color: var(--accent-dark); text-decoration: underline; }
.btn:disabled { opacity: 0.55; cursor: not-allowed; }
.actions { display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: center; margin-top: 0.5rem; }

/* ---------- results ---------- */
.results-head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; gap: 0.5rem; }
.results-head h2 { margin: 0; }
.summary {
  margin: 0.75rem 0;
  padding: 0.75rem 0.9rem;
  background: var(--accent-soft);
  border-left: 4px solid var(--accent);
  border-radius: 6px;
  font-weight: 600;
}
.recap { color: var(--muted); font-size: 0.95rem; }
.card { border: 1px solid var(--line-soft); border-radius: 8px; padding: 0.85rem 1rem; margin: 0 0 1rem; }
.card h3 { margin-top: 0; }
.facts { margin: 0; display: grid; gap: 0.35rem; }
.facts div { display: grid; grid-template-columns: minmax(8rem, 40%) 1fr; gap: 0.5rem; }
.facts dt { color: var(--muted); }
.facts dd { margin: 0; }
.muted { color: var(--muted); font-size: 0.9rem; }
.cut-list, .steps { margin: 0 0 0.5rem; padding-left: 1.25rem; }
.cut-list li, .steps li { margin-bottom: 0.3rem; }
.note { font-size: 0.875rem; color: var(--muted); }
.diagram { margin: 0 0 1rem; }
.diagram svg { display: block; width: 100%; height: auto; max-height: 420px; }
.diagram figcaption { font-size: 0.875rem; color: var(--muted); margin-top: 0.4rem; }

/* ---------- guide + footer ---------- */
.guide { max-width: 72ch; margin-top: 1.5rem; }
.guide ul, .guide ol { padding-left: 1.25rem; }
.guide li { margin-bottom: 0.35rem; }
.site-foot { border-top: 1px solid var(--line-soft); margin-top: 2.5rem; padding-top: 1rem; font-size: 0.875rem; color: var(--muted); }

@media (max-width: 380px) {
  .wrap { padding: 0.75rem; }
  .tool-form, .results { padding: 0.75rem; }
  .facts div { grid-template-columns: 1fr; gap: 0; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; scroll-behavior: auto !important; }
}

@media print {
  body { background: #fff; font-size: 11pt; }
  .wrap { max-width: none; padding: 0; }
  .skip-link, .lede, .tool-form, .guide, .site-foot, #print, noscript { display: none !important; }
  .tool { display: block; }
  .results { border: 0; padding: 0; }
  .summary { background: none; border: 1px solid #000; }
  .card { break-inside: avoid; border-color: #999; }
  .diagram { break-inside: avoid; }
  .diagram svg { max-height: 9cm; }
}