:root {
  --bg: #fbfaf7;
  --fg: #1d1d1b;
  --muted: #5f5e58;
  --accent: #1f5f8b;
  --rule: #d9d6cc;
  --ok: #2e7d32;
  --nok: #c62828;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #161615;
    --fg: #ecebe6;
    --muted: #a9a79f;
    --accent: #7fb6dc;
    --rule: #3a3936;
    --ok: #81c784;
    --nok: #ef9a9a;
  }
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 17px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

a { color: var(--accent); }

.site-header, main, .site-footer {
  max-width: 46rem;
  margin: 0 auto;
  padding: 0 16px;
}

.site-header nav {
  display: flex;
  gap: 1.5rem;
  align-items: baseline;
  padding: 1rem 0;
  border-bottom: 1px solid var(--rule);
}

.site-header .brand {
  margin-right: auto;
  color: var(--fg);
  font-weight: 700;
  text-decoration: none;
}

h1 { font-size: 2rem; line-height: 1.2; margin: 2rem 0 1rem; }
h2 { font-size: 1.25rem; margin: 2rem 0 0.5rem; }
.lead { font-size: 1.25rem; }
.reference { color: var(--muted); font-size: 0.9rem; }

.tex-display { display: block; margin: 1rem 0; overflow-x: auto; text-align: center; }

.curve-plot { margin: 1rem 0; }
.curve-plot svg { display: block; width: 100%; height: auto; }
.curve-plot .axis { stroke: var(--rule); stroke-width: 1; }
.curve-plot .curve { fill: none; stroke: var(--accent); stroke-width: 2.5; }
.curve-plot figcaption { color: var(--muted); font-size: 0.9rem; }

.status { padding: 0.5rem 0.75rem; border-left: 3px solid var(--rule); }
.status.ok { border-color: var(--ok); }
.status.nok { border-color: var(--nok); }

.site-footer {
  margin-top: 3rem;
  padding-top: 1rem;
  padding-bottom: 2rem;
  border-top: 1px solid var(--rule);
}

.disclaimer { color: var(--muted); font-size: 0.9rem; }

/* Calculator */
main:has(.calc) { max-width: 64rem; }

.calc { margin: 1.5rem 0; }
.calc-body { display: grid; gap: 1.5rem; margin-top: 1.5rem; }
@media (min-width: 900px) {
  .calc-body { grid-template-columns: minmax(16rem, 20rem) 1fr; align-items: start; }
}

/* Picture cards: a swipeable carousel on phones, one row on wide screens */
.picker { margin-bottom: 1rem; }
.picker-label { font-weight: 600; margin-bottom: 0.4rem; }
.card-row {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: minmax(10.5rem, 1fr);
  gap: 0.75rem;
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  padding-bottom: 0.4rem;
}
.card {
  scroll-snap-align: start;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.3rem;
  padding: 0.6rem;
  border: 2px solid var(--rule);
  border-radius: 8px;
  background: var(--bg);
  color: var(--fg);
  font: inherit;
  font-size: 0.85rem;
  line-height: 1.3;
  text-align: center;
  cursor: pointer;
}
.card:hover { border-color: var(--muted); }
.card.selected { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent) inset; }
.card:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.card .sketch { width: 100%; height: auto; max-height: 6.5rem; }

/* Drawings */
.sketch .beam { fill: var(--muted); }
.sketch .support { fill: none; stroke: var(--fg); stroke-width: 1.5; }
.sketch .ground, .sketch .hatch { stroke: var(--fg); stroke-width: 1.5; }
.sketch .load { stroke: var(--nok); stroke-width: 1.5; }
.sketch .load-head { fill: var(--nok); }
.sketch .dim { stroke: var(--muted); stroke-width: 1; }
.sketch .shape { fill: color-mix(in srgb, var(--accent) 35%, transparent); stroke: var(--accent); stroke-width: 1.5; }
.sketch-label { fill: var(--fg); font-size: 12px; font-style: italic; }
.sketch-aligned { display: block; width: 100%; height: auto; }

/* Charts */
.diagrams { display: grid; gap: 0.25rem; }
.chart { margin: 0; }
.chart svg { display: block; width: 100%; height: auto; overflow: visible; }
.chart .grid { stroke: var(--rule); stroke-width: 0.6; }
.chart .zero, .chart .axis { stroke: var(--muted); stroke-width: 1; }
.chart .tick { fill: var(--muted); font-size: 11px; }
.chart .chart-title { fill: var(--fg); font-size: 12px; font-weight: 600; }
.chart .curve { fill: none; stroke: var(--accent); stroke-width: 2; }
.chart .area { fill: color-mix(in srgb, var(--accent) 18%, transparent); }
.chart .marker { fill: var(--accent); }
.chart .max-label { fill: var(--fg); font-size: 11px; font-weight: 600; }
.chart.moment .curve { stroke: #b4581f; }
.chart.moment .area { fill: color-mix(in srgb, #b4581f 18%, transparent); }
.chart.moment .marker { fill: #b4581f; }
.chart.stress .curve { stroke: var(--nok); }
.chart.stress .area { fill: color-mix(in srgb, var(--nok) 15%, transparent); }
.chart.stress .marker { fill: var(--nok); }

.calc fieldset {
  margin: 0 0 1rem;
  padding: 0.75rem 1rem 0.25rem;
  border: 1px solid var(--rule);
  border-radius: 6px;
}
.calc legend { padding: 0 0.25rem; font-weight: 600; }

.calc select, .calc input {
  width: 100%;
  min-height: 2.5rem;
  padding: 0.4rem 0.5rem;
  border: 1px solid var(--rule);
  border-radius: 4px;
  background: var(--bg);
  color: var(--fg);
  font: inherit;
}
.calc select { margin-bottom: 0.75rem; }

.field { margin-bottom: 0.75rem; }
.field label { display: block; font-size: 0.9rem; color: var(--muted); }
.input-unit { display: flex; gap: 0.5rem; align-items: center; }
.input-unit span { min-width: 2.5rem; color: var(--muted); font-size: 0.9rem; }

.calc-results h2:first-child { margin-top: 0; }
.results { width: 100%; border-collapse: collapse; font-size: 0.95rem; }
.results th { text-align: left; font-weight: normal; }
.results th, .results td { padding: 0.3rem 0.4rem; border-bottom: 1px solid var(--rule); }
.results .symbol { color: var(--muted); font-style: italic; }
.results .num { text-align: right; font-variant-numeric: tabular-nums; }

.verdict { margin: 1rem 0; padding: 0.6rem 0.8rem; border-left: 4px solid var(--rule); }
.verdict.ok { border-color: var(--ok); }
.verdict.nok { border-color: var(--nok); }
.verdict.ok strong { color: var(--ok); }
.verdict.nok strong { color: var(--nok); }

.calc-error { padding: 0.6rem 0.8rem; border-left: 4px solid var(--nok); }
.note { color: var(--muted); font-size: 0.9rem; }
.disclaimer-box {
  margin-top: 1.5rem;
  padding: 0.6rem 0.8rem;
  border: 1px solid var(--rule);
  border-radius: 6px;
  font-size: 0.9rem;
}