:root {
  --bg: #f4f6f8;
  --panel: #ffffff;
  --text: #1f2328;
  --muted: #5d6874;
  --line: #dde3e9;
  --accent: #0072b2;
  --alive: #0072b2;
  --dead: #eef1f4;
  --damage: #d55e00;
  --grid-line: #c9d1d9;
  --activity: #009e73;
  --radius: 12px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14171b;
    --panel: #1c2026;
    --text: #e6e8ea;
    --muted: #9aa3ab;
    --line: #2f363e;
    --accent: #56b4e9;
    --alive: #56b4e9;
    --dead: #22272e;
    --damage: #f0a04b;
    --grid-line: #39414a;
    --activity: #3fc8a0;
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 24px 24px 32px;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.5 system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

@media (max-width: 760px) {
  body {
    padding: 16px;
  }
}

header,
main,
footer {
  max-width: 1200px;
  margin: 0 auto;
}

header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 20px;
}

h1 {
  margin: 0;
  font-size: 1.6rem;
  letter-spacing: -0.01em;
}

h2 {
  margin: 0;
  font-size: 0.95rem;
  font-weight: 600;
}

.subtitle {
  margin: 2px 0 0;
  color: var(--muted);
}

.intro {
  margin: 8px 0 0;
  font-size: 0.92rem;
}

.intro .links {
  white-space: nowrap;
  margin-left: 4px;
}

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

/* ---- layout ------------------------------------------------------------- */

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 360px;
  grid-template-areas:
    "board side"
    "settings settings";
  gap: 20px;
  align-items: start;
}

.board {
  grid-area: board;
}

.side {
  grid-area: side;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.settings {
  grid-area: settings;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  align-items: start;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
    grid-template-areas:
      "board"
      "side"
      "settings";
  }
}

.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

/* ---- grid canvas ---------------------------------------------------------- */

#grid {
  display: block;
  width: 100%;
  height: min(72vh, 680px);
  border-radius: 8px;
  cursor: crosshair;
  touch-action: none;
}

#grid.panning {
  cursor: grab;
}

#grid.grabbing {
  cursor: grabbing;
}

.view-tools {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

.view-tools .legend {
  margin-left: auto;
}

.hint {
  margin: 0;
  color: var(--muted);
  font-size: 0.85rem;
}

/* ---- buttons and inputs ------------------------------------------------- */

button {
  font: inherit;
  white-space: nowrap;
  padding: 7px 14px;
  border: 1px solid var(--accent);
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  transition: background-color 0.15s, color 0.15s, border-color 0.15s;
}

button:hover {
  filter: brightness(1.06);
}

button.ghost {
  background: transparent;
  color: var(--text);
  border-color: var(--line);
}

button.ghost:hover {
  border-color: var(--accent);
  filter: none;
}

button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.segmented {
  display: inline-flex;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 2px;
  gap: 2px;
  background: var(--bg);
}

.segmented button {
  border: none;
  background: transparent;
  color: var(--muted);
  border-radius: 6px;
  padding: 5px 12px;
}

.segmented button:hover {
  color: var(--text);
  filter: none;
}

.segmented button[aria-pressed="true"] {
  background: var(--panel);
  color: var(--text);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.15);
}

.buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.slider {
  display: grid;
  grid-template-columns: 64px minmax(0, 1fr) 40px auto;
  align-items: center;
  gap: 8px;
}

.slider input {
  width: 100%;
  accent-color: var(--accent);
}

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

.unit {
  color: var(--muted);
  font-size: 0.85rem;
}

select,
input[type="text"],
input[type="number"] {
  font: inherit;
  padding: 6px 8px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  color: var(--text);
  width: 100%;
  min-width: 0;
}

input[type="text"] {
  font-family: ui-monospace, "Cascadia Mono", Consolas, monospace;
}

.size {
  display: flex;
  align-items: flex-end;
  gap: 8px;
}

.size label {
  display: flex;
  flex-direction: column;
  gap: 2px;
  font-size: 0.85rem;
  color: var(--muted);
  flex: 1;
}

.times {
  color: var(--muted);
  padding-bottom: 7px;
}

.radios {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 16px;
}

.radios label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.radios input {
  accent-color: var(--accent);
}

.note {
  margin: 0;
  color: var(--muted);
  font-size: 0.87rem;
}

.error {
  margin: 0;
  color: var(--damage);
  font-size: 0.87rem;
}

/* ---- measurements ---------------------------------------------------------- */

.metrics {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  margin: 0;
}

.metrics div {
  background: var(--bg);
  border-radius: 8px;
  padding: 6px 10px;
}

.metrics .wide {
  grid-column: 1 / -1;
}

.metrics dt {
  color: var(--muted);
  font-size: 0.8rem;
}

.metrics dd {
  margin: 0;
  font-variant-numeric: tabular-nums;
  font-size: 1.1rem;
}

.tabs {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--line);
}

.tab {
  background: transparent;
  color: var(--muted);
  border: none;
  border-bottom: 2px solid transparent;
  border-radius: 0;
  padding: 6px 10px;
  font-size: 0.88rem;
}

.tab:hover {
  color: var(--text);
  filter: none;
}

.tab[aria-selected="true"] {
  color: var(--text);
  border-bottom-color: var(--accent);
}

.tab-panel {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.chart {
  display: block;
  width: 100%;
  height: 110px;
  border-radius: 8px;
  background: var(--bg);
}

.spacetime {
  display: block;
  width: 100%;
  height: 150px;
  border-radius: 8px;
  image-rendering: pixelated;
}

.legend {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 4px 6px;
  color: var(--muted);
  font-size: 0.82rem;
}

.swatch {
  display: inline-block;
  width: 12px;
  height: 4px;
  border-radius: 2px;
}

.swatch + span + .swatch {
  margin-left: 8px;
}

.swatch.alive {
  background: var(--alive);
}

.swatch.activity {
  background: var(--activity);
}

.swatch.damage {
  background: var(--damage);
}

.usage {
  width: 100%;
  border-collapse: separate;
  border-spacing: 3px;
  font-size: 0.75rem;
  font-variant-numeric: tabular-nums;
}

.usage th {
  color: var(--muted);
  font-weight: 500;
  text-align: center;
}

.usage td {
  height: 28px;
  text-align: center;
  border-radius: 5px;
  border: 1px solid transparent;
  color: var(--text);
}

.usage td.in-rule {
  border: 2px solid var(--accent);
}

.usage td.in-rule.unused {
  border-style: dashed;
}

footer {
  margin-top: 24px;
  font-size: 0.85rem;
}

[hidden] {
  display: none !important;
}