/* Stagemath: a dark console for people who work in dark rooms, with gaffer-tape labels.
   System fonts only. No external resources. Designed for a phone first (375px), right at 1280px. */

:root {
  --ground: #121519;
  --panel: #1b2026;
  --panel-2: #232a32;
  --line: #3a434d;
  --ink: #efece2;
  --muted: #b2bac3;
  --amber: #ffb400;
  --amber-ink: #14110a;
  --focus: #7fd4ff;
  --alert: #ff9a8a;
  --tape: #e9e4d3;
  --tape-ink: #16181b;
  --display: #0b0d10;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

/* Lit rooms and daylight: a paper-ground variant. The readout stays dark in both. */
@media (prefers-color-scheme: light) {
  :root {
    --ground: #f1eee5;
    --panel: #fbfaf5;
    --panel-2: #e8e4d7;
    --line: #8d8a7d;
    --ink: #16181b;
    --muted: #444b53;
    --focus: #0b5fa8;
    --alert: #a3281a;
  }
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--ground);
  color: var(--ink);
  font: 16px/1.5 var(--sans);
}
.wrap { width: 100%; max-width: 1120px; margin: 0 auto; padding: 0 16px; }
.vh { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
a { color: inherit; text-underline-offset: 3px; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; }
.skip { position: absolute; left: 8px; top: -60px; background: var(--amber); color: var(--amber-ink); padding: 12px 16px; font-weight: 700; z-index: 10; }
.skip:focus { top: 8px; }

/* ---------- Bar ---------- */
.bar { border-bottom: 1px solid var(--line); background: var(--ground); }
.bar-in { display: flex; align-items: center; justify-content: space-between; min-height: 52px; }
.brand { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; min-height: 44px; }
.brand-mark { width: 26px; height: 26px; color: var(--amber); }
@media (prefers-color-scheme: light) { .brand-mark { color: var(--tape-ink); } }
.brand-name { font: 700 15px/1 var(--mono); letter-spacing: .14em; }
.bar-nav { display: none; gap: 20px; font-size: 15px; }
.bar-nav a { display: inline-flex; align-items: center; min-height: 44px; }

/* ---------- Hero ---------- */
.hero { padding: 14px 0 28px; }
.hero-grid { display: grid; gap: 14px; }
.tape {
  display: inline-block; margin: 0 0 8px; padding: 3px 8px;
  background: var(--tape); color: var(--tape-ink);
  font: 700 11px/1.3 var(--mono); letter-spacing: .12em;
  transform: rotate(-1deg); border-radius: 1px;
}
.headline { margin: 0 0 8px; font: 800 24px/1.15 var(--sans); letter-spacing: -.01em; }
.subhead { margin: 0; font-size: 15px; line-height: 1.4; color: var(--muted); }
.subhead strong { color: var(--ink); }
.terms, .contrast-line { display: none; }

/* ---------- Console ---------- */
.console { background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 10px; }

.tabs { display: grid; grid-template-columns: repeat(5, 1fr); gap: 4px; }
.tabs button {
  min-height: 48px; padding: 4px 2px;
  font: 700 13px/1.1 var(--sans); letter-spacing: .01em;
  background: var(--panel-2); color: var(--ink);
  border: 1px solid var(--line); border-radius: 6px; cursor: pointer;
  hyphens: manual;
}
.tabs button[aria-selected="true"] { background: var(--tape); color: var(--tape-ink); border-color: var(--tape); }

.units { display: flex; align-items: center; gap: 6px; margin: 8px 0 2px; }
.units-label { font: 700 11px/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin-right: 4px; }
.seg { position: relative; display: inline-flex; }
.seg input { position: absolute; opacity: 0; inset: 0; width: 100%; height: 100%; margin: 0; cursor: pointer; }
.seg span {
  display: inline-flex; align-items: center; justify-content: center; min-height: 44px; padding: 0 14px;
  font: 600 14px/1 var(--mono); border: 1px solid var(--line); border-radius: 6px; background: var(--panel-2);
}
.seg input:checked + span { background: var(--tape); color: var(--tape-ink); border-color: var(--tape); }
.seg input:focus-visible + span { outline: 3px solid var(--focus); outline-offset: 2px; }

.panel[hidden] { display: none; }
.panel-sub { margin: 6px 0 8px; font-size: 14px; color: var(--muted); line-height: 1.35; }

.form { margin: 0; }
.row { display: grid; gap: 8px; }
.row-2 { grid-template-columns: 1fr 1fr; }
.row-3 { grid-template-columns: 1fr 1fr 1fr; }
.row-4 { grid-template-columns: 1fr 1fr; }
.field { display: flex; flex-direction: column; margin-bottom: 8px; min-width: 0; }
.field label { font: 700 12px/1.25 var(--sans); letter-spacing: .03em; margin-bottom: 4px; min-height: 30px; display: flex; align-items: flex-end; }
.opt { font-weight: 400; color: var(--muted); margin-left: 4px; }
.field input {
  width: 100%; min-height: 48px; padding: 8px 10px;
  font: 600 20px/1.2 var(--mono); color: var(--ink);
  background: var(--display); border: 1px solid var(--line); border-radius: 6px;
}
.field input::placeholder { color: #8b949e; font-weight: 400; opacity: 1; }
@media (prefers-color-scheme: light) {
  .field input { background: #fff; }
  .field input::placeholder { color: #666d75; }
}
.field-opt { max-width: 50%; }
.row-3 .field label, .row-4 .field label { font-size: 11.5px; }

.err { margin: 0 0 8px; padding: 8px 10px; font-size: 14px; color: var(--alert); border-left: 4px solid var(--alert); background: var(--display); }
@media (prefers-color-scheme: light) { .err { background: #fff; } }

.form-actions { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 10px; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; min-height: 52px; padding: 0 18px;
  font: 700 16px/1.1 var(--sans); border-radius: 6px; border: 2px solid transparent; cursor: pointer; text-decoration: none;
}
.btn-primary { background: var(--amber); color: var(--amber-ink); flex: 1 1 200px; }
.btn-primary:hover { background: #ffc43a; }
.btn-quiet { background: transparent; color: var(--ink); border-color: var(--line); min-height: 48px; font-weight: 600; font-size: 15px; }
.btn-quiet:hover { border-color: var(--ink); }

/* ---------- Readout: always a dark display with amber digits ---------- */
.readout {
  background: var(--display); color: #efece2; border: 1px solid #2c343d; border-radius: 8px; padding: 12px 14px 10px;
}
.readout-head { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.chip { font: 700 11px/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; padding: 5px 7px; border-radius: 2px; background: #efece2; color: #16181b; }
.chip-live { background: var(--amber); color: var(--amber-ink); }
.readout-for { font-size: 13px; color: #b2bac3; }
.big { margin: 6px 0 0; display: flex; align-items: baseline; gap: 8px; line-height: 1; }
.big .num { font: 700 56px/1 var(--mono); color: var(--amber); letter-spacing: -.02em; }
.big .unit { font: 600 20px/1 var(--mono); color: #efece2; }
.big-label { margin: 4px 0 8px; font: 700 12px/1.2 var(--mono); letter-spacing: .1em; text-transform: uppercase; color: #b2bac3; }
.diagram { display: none; width: 100%; max-width: 360px; height: auto; color: #b2bac3; margin: 0 0 6px; }
.readout-rows { margin: 0; border-top: 1px solid #2c343d; }
.readout-rows div { display: flex; justify-content: space-between; gap: 12px; padding: 7px 0; border-bottom: 1px solid #2c343d; font-size: 14px; }
.readout-rows dt { color: #b2bac3; }
.readout-rows dd { margin: 0; font: 600 14px/1.3 var(--mono); text-align: right; }
.caveat { margin: 8px 0 0; font-size: 13px; line-height: 1.4; color: #b2bac3; }
.readout-foot { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-top: 10px; }
.readout .btn-quiet { color: #efece2; border-color: #4a5560; }
.readout .btn-quiet:hover { border-color: #efece2; }
.readout :focus-visible { outline-color: #7fd4ff; }
.readout-note { font-size: 13px; color: #b2bac3; }

/* ---------- Success ---------- */
.done { display: flex; gap: 12px; margin-top: 10px; padding: 12px; border: 2px solid var(--amber); border-radius: 8px; background: var(--panel-2); }
.done[hidden] { display: none; }
.done-icon { flex: none; width: 28px; height: 28px; color: var(--amber); margin-top: 2px; }
@media (prefers-color-scheme: light) { .done-icon { color: var(--tape-ink); } }
.done-body p { margin: 0 0 6px; font-size: 15px; }
.done-title { font-weight: 800; font-size: 16px !important; }
.ask a { font-weight: 700; }

/* ---------- Sections ---------- */
.section { padding: 28px 0; border-top: 1px solid var(--line); }
.section-alt { background: var(--panel); }
.section-title { margin: 0 0 8px; font: 800 22px/1.2 var(--sans); }
.section-lede { margin: 0 0 14px; color: var(--muted); max-width: 62ch; }
.compare-wrap { overflow-x: auto; }
.compare { width: 100%; border-collapse: collapse; font-size: 15px; min-width: 520px; }
.compare caption { text-align: left; font-size: 13px; color: var(--muted); padding-bottom: 10px; caption-side: top; }
.compare th, .compare td { padding: 10px 10px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
.compare thead th { font: 700 12px/1.2 var(--mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.compare tbody th { font-weight: 700; width: 24%; }
.compare .ours { background: var(--panel-2); }
.compare thead .ours { color: var(--ink); }
.compare .dim { color: var(--muted); }
.note { margin: 12px 0 0; font-size: 14px; color: var(--muted); max-width: 66ch; }

.facts { margin: 0; display: grid; gap: 14px; }
.facts dt { font: 700 12px/1.2 var(--mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); margin-bottom: 4px; }
.facts dd { margin: 0; max-width: 62ch; }

.foot { border-top: 1px solid var(--line); padding: 20px 0 32px; font-size: 14px; color: var(--muted); }
.foot p { margin: 0 0 6px; }
.foot a { color: var(--ink); font-weight: 700; }

/* ---------- Wide ---------- */
@media (min-width: 400px) {
  .headline { font-size: 26px; }
  .row-4 { grid-template-columns: repeat(4, 1fr); }
}
@media (min-width: 720px) {
  .wrap { padding: 0 28px; }
  .bar-nav { display: flex; }
  .hero { padding: 40px 0 56px; }
  .hero-grid { grid-template-columns: 5fr 7fr; gap: 48px; align-items: start; }
  .tape { font-size: 12px; margin-bottom: 14px; }
  .headline { font-size: 40px; line-height: 1.08; margin-bottom: 14px; }
  .subhead { font-size: 18px; margin-bottom: 20px; }
  .terms { display: block; margin: 0 0 20px; border-top: 1px solid var(--line); }
  .terms div { display: flex; justify-content: space-between; padding: 10px 0; border-bottom: 1px solid var(--line); }
  .terms dt { color: var(--muted); }
  .terms dd { margin: 0; font: 700 15px/1.3 var(--mono); }
  .contrast-line { display: block; margin: 0; color: var(--muted); font-size: 15px; }
  .contrast-line a { color: var(--ink); font-weight: 700; }
  .console { padding: 18px; border-radius: 12px; }
  .tabs button { font-size: 15px; }
  .panel-sub { font-size: 15px; }
  .diagram { display: block; }
  .big .num { font-size: 72px; }
  .btn-primary { flex: 0 1 auto; }
  .section { padding: 48px 0; }
  .section-title { font-size: 28px; }
  .facts { grid-template-columns: 1fr 1fr; gap: 24px 48px; }
}
@media (min-width: 1000px) {
  .hero-grid { gap: 72px; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }
@media print { .bar, .tabs, .units, .form-actions, .skip { display: none; } body { background: #fff; color: #000; } }