/* QuantityMath — base stylesheet
   Mobile-first, no frameworks, no external requests. */

:root {
  --bg: #ffffff;
  --bg-soft: #f5f7fa;
  --surface: #ffffff;
  --border: #dfe3e8;
  --text: #16202b;
  --muted: #5b6b7c;
  --accent: #1f6feb;
  --accent-dark: #17539e;
  --accent-soft: #eaf1fd;
  --good: #0f7b4f;
  --shadow: 0 1px 2px rgba(16, 32, 48, .06), 0 6px 20px rgba(16, 32, 48, .06);
  --radius: 12px;
  --wrap: 1080px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1419;
    --bg-soft: #161c23;
    --surface: #161c23;
    --border: #2a3440;
    --text: #e8edf2;
    --muted: #9aa8b6;
    --accent: #4d94ff;
    --accent-dark: #7db0ff;
    --accent-soft: #17263c;
    --good: #4ecb8f;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 6px 20px rgba(0, 0, 0, .3);
  }
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.wrap { width: 100%; max-width: var(--wrap); margin: 0 auto; padding: 0 20px; }

.skip {
  position: absolute; left: -9999px;
  background: var(--accent); color: #fff; padding: 10px 16px; border-radius: 0 0 var(--radius) 0;
}
.skip:focus { left: 0; top: 0; z-index: 100; }

/* ---------- Header ---------- */

.site-header {
  border-bottom: 1px solid var(--border);
  background: var(--bg);
  position: sticky; top: 0; z-index: 20;
}
.site-header .wrap {
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; min-height: 62px; flex-wrap: wrap;
}
.brand {
  font-weight: 750; font-size: 1.15rem; letter-spacing: -.02em;
  color: var(--text); text-decoration: none;
}
.brand span { color: var(--accent); }
.site-header nav { display: flex; gap: 20px; flex-wrap: wrap; }
.site-header nav a {
  color: var(--muted); text-decoration: none; font-size: .92rem; font-weight: 550;
}
.site-header nav a:hover { color: var(--accent); }

/* ---------- Hero ---------- */

.hero { background: var(--bg-soft); border-bottom: 1px solid var(--border); padding: 44px 0 40px; }
.hero h1 { margin: 0 0 10px; font-size: clamp(1.9rem, 5vw, 2.6rem); letter-spacing: -.03em; line-height: 1.15; }
.lede { margin: 0; max-width: 62ch; color: var(--muted); font-size: 1.06rem; }

/* ---------- Calculator ---------- */

.calc-section { padding: 40px 20px 8px; }

.calc-grid {
  display: grid; gap: 18px;
  grid-template-columns: 1fr;
  margin-bottom: 26px;
}
@media (min-width: 760px) {
  .calc-grid { grid-template-columns: repeat(3, 1fr); }
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  margin: 0;
  min-width: 0;
}
.card legend {
  font-weight: 700; font-size: .82rem; text-transform: uppercase;
  letter-spacing: .06em; color: var(--accent);
  padding: 0 6px;
}

label {
  display: block; margin: 14px 0 6px;
  font-size: .88rem; font-weight: 600; color: var(--text);
}
.card label:first-of-type { margin-top: 4px; }

input[type="number"], select {
  width: 100%;
  padding: 11px 12px;
  font: inherit; font-size: 1rem;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  appearance: none;
  transition: border-color .12s, box-shadow .12s;
}
select {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8'%3E%3Cpath fill='%235b6b7c' d='M6 8 0 0h12z'/%3E%3C/svg%3E");
  background-repeat: no-repeat; background-position: right 12px center; padding-right: 34px;
}
input[type="number"]:focus, select:focus {
  outline: none; border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.check {
  display: flex; align-items: center; gap: 10px;
  margin-top: 16px; font-weight: 600; cursor: pointer;
}
.check input { width: 18px; height: 18px; accent-color: var(--accent); flex: 0 0 auto; }
.check span { font-size: .9rem; }

.hint { margin: 14px 0 0; font-size: .82rem; color: var(--muted); line-height: 1.5; }

/* ---------- Results ---------- */

.results {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}
.results h2 {
  margin: 0 0 4px; font-size: 1.02rem; text-transform: uppercase;
  letter-spacing: .06em; color: var(--accent);
}
.results .sub { margin: 0 0 20px; font-size: .86rem; color: var(--muted); }

.headline {
  display: flex; flex-wrap: wrap; align-items: baseline; gap: 10px;
  padding-bottom: 18px; margin-bottom: 18px; border-bottom: 1px solid var(--border);
}
.headline .big { font-size: clamp(2.1rem, 7vw, 2.9rem); font-weight: 750; letter-spacing: -.03em; line-height: 1; }
.headline .unit { font-size: 1.05rem; color: var(--muted); font-weight: 600; }

.rows { display: grid; gap: 0; margin: 0 0 18px; }
.row {
  display: flex; justify-content: space-between; align-items: baseline;
  gap: 16px; padding: 9px 0; border-bottom: 1px dashed var(--border);
}
.row:last-child { border-bottom: 0; }
.row .k { color: var(--muted); font-size: .92rem; }
.row .v { font-weight: 700; font-variant-numeric: tabular-nums; white-space: nowrap; }
.row.total { border-top: 2px solid var(--border); border-bottom: 0; margin-top: 6px; padding-top: 14px; }
.row.total .k { color: var(--text); font-weight: 700; font-size: 1rem; }
.row.total .v { color: var(--good); font-size: 1.22rem; }

.buy {
  background: var(--accent-soft);
  border-radius: 9px; padding: 16px 18px;
}
.buy h3 { margin: 0 0 10px; font-size: .95rem; }
.buy ul { margin: 0; padding-left: 20px; }
.buy li { margin: 5px 0; font-size: .92rem; }

.results .error {
  margin: 0; color: #b3261e; font-weight: 600;
}
@media (prefers-color-scheme: dark) { .results .error { color: #ff8a80; } }

.disclaimer { margin: 18px 0 0; font-size: .84rem; color: var(--muted); max-width: 78ch; }

/* ---------- Prose ---------- */

.prose { padding: 46px 20px 0; max-width: 860px; }
.prose h2 {
  margin: 34px 0 12px; font-size: clamp(1.3rem, 3.4vw, 1.6rem);
  letter-spacing: -.02em; line-height: 1.25;
}
.prose h2:first-child { margin-top: 0; }
.prose h3 { margin: 24px 0 8px; font-size: 1.06rem; }
.prose p, .prose li { color: var(--text); }
.prose ol, .prose ul { padding-left: 22px; }
.prose li { margin: 8px 0; }
.prose a { color: var(--accent); }

.cta {
  margin: 52px auto 0; padding: 28px 20px;
  background: var(--bg-soft); border: 1px solid var(--border);
  border-radius: var(--radius); max-width: 860px;
}
.cta h2 { margin: 0 0 8px; font-size: 1.2rem; }
.cta p { margin: 0; color: var(--muted); }

/* ---------- Footer ---------- */

.site-footer {
  margin-top: 56px; padding: 32px 0 40px;
  border-top: 1px solid var(--border); background: var(--bg-soft);
}
.foot-brand { margin: 0 0 10px; font-weight: 750; }
.site-footer nav { display: flex; gap: 18px; flex-wrap: wrap; margin-bottom: 16px; }
.site-footer nav a { color: var(--muted); text-decoration: none; font-size: .9rem; }
.site-footer nav a:hover { color: var(--accent); }
.disclosure, .copy { margin: 0 0 10px; font-size: .82rem; color: var(--muted); max-width: 80ch; line-height: 1.55; }

/* ---------- Accessibility helpers ---------- */

.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

/* ---------- Breadcrumbs ---------- */

.crumbs {
  font-size: .84rem; color: var(--muted); margin-bottom: 12px;
}
.crumbs a { color: var(--muted); text-decoration: none; }
.crumbs a:hover { color: var(--accent); text-decoration: underline; }
.crumbs span[aria-hidden] { margin: 0 6px; opacity: .6; }

/* ---------- Direct answer box (feeds featured snippets and AI answers) ---------- */

.answer {
  margin-top: 20px; padding: 16px 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.answer p { margin: 0 0 10px; }
.answer p:last-child { margin-bottom: 0; }

/* ---------- Quick-answer table ---------- */

.tablewrap {
  max-width: 860px; margin: 44px auto 0; padding: 0 20px;
  overflow-x: auto;
}
.tablewrap h2 {
  margin: 0 0 14px; font-size: clamp(1.2rem, 3.2vw, 1.45rem);
  letter-spacing: -.02em;
}
table.quick {
  width: 100%; border-collapse: collapse; font-size: .92rem;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); overflow: hidden;
}
table.quick th, table.quick td {
  padding: 11px 14px; text-align: left; border-bottom: 1px solid var(--border);
  white-space: nowrap;
}
table.quick thead th {
  background: var(--bg-soft); font-size: .78rem; text-transform: uppercase;
  letter-spacing: .05em; color: var(--muted); font-weight: 700;
}
table.quick tbody th { font-weight: 600; white-space: normal; min-width: 220px; }
table.quick td { font-variant-numeric: tabular-nums; }
table.quick tbody tr:last-child th, table.quick tbody tr:last-child td { border-bottom: 0; }
table.quick tbody tr:hover { background: var(--accent-soft); }
.note { margin: 12px 0 0; font-size: .82rem; color: var(--muted); line-height: 1.55; }

/* ---------- Content blocks ---------- */

.block { max-width: 860px; margin: 46px auto 0; padding: 0 20px; }
.block h2 {
  margin: 0 0 12px; font-size: clamp(1.25rem, 3.3vw, 1.5rem);
  letter-spacing: -.02em; line-height: 1.25;
}
.block h3 { margin: 22px 0 8px; font-size: 1.05rem; }
.block p, .block li { color: var(--text); }
.block ol, .block ul { padding-left: 22px; }
.block li { margin: 7px 0; }

/* ---------- FAQ accordion ---------- */

details.qa {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); margin: 10px 0; overflow: hidden;
}
details.qa summary {
  cursor: pointer; padding: 14px 18px; font-weight: 650;
  list-style: none; position: relative; padding-right: 44px;
}
details.qa summary::-webkit-details-marker { display: none; }
details.qa summary::after {
  content: '+'; position: absolute; right: 18px; top: 50%;
  transform: translateY(-50%); font-size: 1.3rem; font-weight: 400; color: var(--accent);
}
details.qa[open] summary::after { content: '−'; }
details.qa summary:hover { background: var(--bg-soft); }
details.qa .a { padding: 0 18px 14px; }
details.qa .a p { margin: 0; color: var(--muted); }

/* ---------- Link lists (internal linking) ---------- */

ul.linklist {
  list-style: none; padding: 0; margin: 0;
  display: grid; gap: 8px; grid-template-columns: 1fr;
}
@media (min-width: 700px) { ul.linklist { grid-template-columns: 1fr 1fr; } }
ul.linklist li { margin: 0; }
ul.linklist a {
  display: block; padding: 12px 16px; text-decoration: none;
  color: var(--text); background: var(--surface);
  border: 1px solid var(--border); border-radius: 9px;
  font-size: .93rem; font-weight: 550;
}
ul.linklist a:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); }

.related ul { list-style: none; padding: 0; margin: 0; }
.related li { margin: 9px 0; }
.related a { color: var(--accent); text-decoration: none; font-weight: 550; }
.related a:hover { text-decoration: underline; }