:root {
  color-scheme: light dark;

  --page-background: #f3f1ec;
  --page-text: #20232a;
  --muted-text: #5f6670;
  --panel-background: #ffffff;
  --panel-border: #d9d4ca;
  --accent: #2f6fde;
  --accent-text: #ffffff;
  --radius: 0.5rem;
  --gap: 1rem;

  /* Canvas drawing: read by js/renderer.js */
  --ground: #a9c495;
  --road-surface: #5c5f66;
  --road-edge: #f4f4f4;
  --lane-marking: #f4f4f4;
  --choke-marking: #ffcc33;
  --car-colors: #e6194b, #3cb44b, #ffe119, #4363d8, #f58231, #911eb4, #42d4f4, #f032e6,
    #bfef45, #fabed4, #469990, #dcbeff, #9a6324, #fffac8, #aaffc3, #ffd8b1;
  --car-outline: #1b1b1b;
  --exit-marker: #ffffff;
  --max-lane-height: 30;    /* px */
  --road-padding: 8;        /* px */
  --car-size: 0.36;         /* radius as a fraction of lane height */
  --line-width: 1;          /* px */
  --exit-marker-width: 2;   /* px */
  --lane-dash: 8 10;        /* px */
}

@media (prefers-color-scheme: dark) {
  :root {
    --page-background: #16181c;
    --page-text: #e6e8eb;
    --muted-text: #9aa1ab;
    --panel-background: #1f2228;
    --panel-border: #343841;
    --accent: #6d9bf0;
    --accent-text: #0d1117;

    --ground: #2c3a27;
    --road-surface: #43464d;
    --road-edge: #d8d8d8;
    --lane-marking: #bdbdbd;
    --car-outline: #0b0b0b;
  }
}

[hidden] {
  display: none !important;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: var(--gap);
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  line-height: 1.4;
  background: var(--page-background);
  color: var(--page-text);
}

header {
  margin-bottom: var(--gap);
}

h1 {
  margin: 0;
  font-size: 1.6rem;
}

header p,
fieldset p {
  margin: 0;
  color: var(--muted-text);
}

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

h2 {
  margin: 0;
  font-size: 1rem;
}

main {
  display: grid;
  grid-template-columns: minmax(15rem, 19rem) minmax(0, 1fr);
  grid-template-rows: auto auto 1fr;
  gap: var(--gap);
  align-items: start;
}

form {
  grid-row: 1 / -1;
  display: grid;
  gap: var(--gap);
}

fieldset {
  display: grid;
  gap: 0.75rem;
  margin: 0;
  padding: 0.75rem var(--gap) var(--gap);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  background: var(--panel-background);
}

legend {
  padding: 0 0.25rem;
  font-weight: 600;
}

fieldset p {
  font-size: 0.85rem;
}

label {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: 0.25rem 0.5rem;
}

label > input[type="range"] {
  grid-column: 1 / -1;
  width: 100%;
}

input[type="number"] {
  width: 5em;
}

input,
select,
button {
  font: inherit;
}

input[type="range"] {
  accent-color: var(--accent);
}

output {
  font-variant-numeric: tabular-nums;
}

fieldset div {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

button {
  padding: 0.35rem 0.8rem;
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  background: var(--accent);
  color: var(--accent-text);
  cursor: pointer;
}

button:disabled {
  opacity: 0.4;
  cursor: default;
}

dl {
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 1.25rem;
  margin: 0;
}

dl div {
  display: flex;
  gap: 0.4rem;
}

dt {
  color: var(--muted-text);
}

dt::after {
  content: ":";
}

dd {
  margin: 0;
  font-variant-numeric: tabular-nums;
}

figure {
  display: grid;
  gap: 0.5rem;
  margin: 0;
  padding: 0.75rem;
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  background: var(--panel-background);
}

canvas {
  display: block;
  width: 100%;
  height: clamp(8rem, 26vh, 16rem);
  border-radius: calc(var(--radius) / 2);
  background: var(--ground);
}

figcaption {
  display: grid;
  gap: 0.25rem;
  font-size: 0.9rem;
}

@media (max-width: 52rem) {
  main {
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: none;
  }

  form {
    grid-row: auto;
  }
}