:root {
  color-scheme: dark;

  --bg: #0a0d0b;
  --panel: #0e1210;
  --rail: #0c100e;
  --line: #1b221d;
  --line-bright: #2a332c;
  --ink: #cfdad0;
  --muted: #77867a;
  --accent: #6ee787;
  --accent-dim: #1b3a26;
  --accent-ink: #05130a;
  --danger: #ff7b72;

  --canvas: #070a08;
  --canvas-grid: #131a15;
  --cell: #b6ff6a;
  --cell-ghost: #23331d;

  --mono: ui-monospace, "SF Mono", "JetBrains Mono", "Cascadia Code", Menlo, Consolas, monospace;
  --topbar: 44px;
  --gap: 18px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  display: grid;
  grid-template-rows: var(--topbar) auto;
  min-height: 100dvh;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

button,
input,
textarea,
progress {
  font: inherit;
  color: inherit;
}

a {
  color: var(--muted);
  text-decoration: none;
  border-bottom: 1px solid var(--line-bright);
}

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

:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 2px;
}

.skip {
  position: fixed;
  top: 8px;
  left: 8px;
  z-index: 5;
  padding: 6px 10px;
  background: var(--accent);
  color: var(--accent-ink);
  transform: translateY(-200%);
}

.skip:focus {
  transform: none;
}

/* topbar */

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 0 14px;
  border-bottom: 1px solid var(--line);
  background: var(--panel);
}

.brand,
.topbar-meta,
.engine {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 0;
}

h1 {
  margin: 0;
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.02em;
}

.glider {
  display: grid;
  grid-template: repeat(3, 4px) / repeat(3, 4px);
  gap: 1px;
}

/* the five cells of a glider, in reading order of the 3x3 box */
.glider i:nth-child(1) {
  grid-area: 1 / 2;
}
.glider i:nth-child(2) {
  grid-area: 2 / 3;
}
.glider i:nth-child(3) {
  grid-area: 3 / 1;
}
.glider i:nth-child(4) {
  grid-area: 3 / 2;
}
.glider i:nth-child(5) {
  grid-area: 3 / 3;
}

.glider i {
  background: var(--cell);
}

.engine {
  gap: 7px;
  color: var(--muted);
  font-size: 11px;
}

.led {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--muted);
}

.engine[data-state="ready"] .led {
  background: var(--accent);
  box-shadow: 0 0 6px var(--accent);
}

.engine[data-state="error"] .led {
  background: var(--danger);
}

/* layout */

/* the app owns the first screen exactly; the write-up starts below the fold */
main {
  display: grid;
  grid-template-rows: calc(100dvh - var(--topbar)) auto;
  min-height: 0;
}

.layout {
  display: grid;
  grid-template-columns: 268px minmax(0, 1fr);
  min-height: 0;
}

.rail {
  display: flex;
  flex-direction: column;
  gap: var(--gap);
  padding: var(--gap) 16px 24px;
  overflow-y: auto;
  border-right: 1px solid var(--line);
  background: var(--rail);
}

.panel {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin: 0;
  padding: 0 0 var(--gap);
  border: 0;
  border-bottom: 1px solid var(--line);
}

legend,
label,
.stat > span {
  color: var(--muted);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

legend {
  padding: 0;
  margin-bottom: 10px;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.triple {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 6px;
}

label output {
  color: var(--ink);
  letter-spacing: 0;
  text-transform: none;
}

/* controls */

.segmented {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  border: 1px solid var(--line-bright);
}

.segmented input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.segmented label {
  padding: 7px 4px;
  text-align: center;
  cursor: pointer;
}

.segmented input + label:not(:first-of-type) {
  border-left: 1px solid var(--line-bright);
}

.segmented input:checked + label {
  background: var(--accent-dim);
  color: var(--accent);
}

.segmented input:focus-visible + label {
  outline: 1px solid var(--accent);
  outline-offset: -2px;
}

textarea,
input[type="number"] {
  width: 100%;
  padding: 8px 9px;
  border: 1px solid var(--line-bright);
  background: var(--bg);
  resize: vertical;
}

textarea:focus,
input[type="number"]:focus {
  border-color: var(--accent);
  outline: none;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
  cursor: pointer;
}

input[type="checkbox"] {
  accent-color: var(--accent);
  margin: 0;
}

.check {
  display: flex;
  align-items: center;
  gap: 7px;
  cursor: pointer;
  text-transform: none;
  letter-spacing: 0;
}

.btn,
.tool {
  padding: 8px 10px;
  border: 1px solid var(--line-bright);
  background: transparent;
  cursor: pointer;
  white-space: nowrap;
}

.btn:hover:not(:disabled),
.tool:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent);
}

.btn:disabled,
.tool:disabled {
  color: var(--muted);
  cursor: not-allowed;
  opacity: 0.5;
}

.btn.primary {
  border-color: var(--accent);
  background: var(--accent);
  color: var(--accent-ink);
}

.btn.primary:hover:not(:disabled) {
  background: transparent;
  color: var(--accent);
}

.meta {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  margin: -4px 0 0;
  color: var(--muted);
  font-size: 11px;
}

progress {
  width: 100%;
  height: 4px;
  border: 0;
  background: var(--line);
}

progress::-webkit-progress-bar {
  background: var(--line);
}

progress::-webkit-progress-value {
  background: var(--accent);
}

progress::-moz-progress-bar {
  background: var(--accent);
}

.error {
  margin: 0;
  padding: 9px 10px;
  border-left: 2px solid var(--danger);
  background: color-mix(in srgb, var(--danger) 8%, transparent);
  color: var(--danger);
  font-size: 11px;
}

.keys {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 4px 12px;
  margin: auto 0 0;
  color: var(--muted);
  font-size: 11px;
}

.keys dt,
.keys dd {
  margin: 0;
}

kbd {
  font: inherit;
  color: var(--ink);
}

/* stage */

.stage {
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
  min-width: 0;
}

.stage-bar,
.stage-status {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 8px 14px;
  background: var(--panel);
}

.stage-bar {
  min-height: 41px;
  border-bottom: 1px solid var(--line);
}

.views,
.tools {
  display: flex;
  align-items: center;
  gap: 6px;
}

.tools {
  margin-left: auto;
}

.tool {
  min-width: 30px;
  padding: 5px 9px;
  font-size: 11px;
}

.tool[aria-pressed="true"] {
  border-color: var(--accent);
  background: var(--accent-dim);
  color: var(--accent);
}

.canvas-wrap {
  position: relative;
  overflow: hidden;
  background: var(--canvas);
  cursor: grab;
  touch-action: none;
}

.canvas-wrap.drawing {
  cursor: crosshair;
}

.canvas-wrap.panning {
  cursor: grabbing;
}

canvas {
  display: block;
  width: 100%;
  height: 100%;
}

/* faint scanlines over the board, for the phosphor look */
.canvas-wrap::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: repeating-linear-gradient(
    to bottom,
    rgb(255 255 255 / 2.5%) 0 1px,
    transparent 1px 3px
  );
}

.boot {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  margin: 0;
  background: var(--canvas);
  color: var(--accent);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.boot span::after {
  content: "";
  animation: dots 1.2s steps(4, end) infinite;
}

@keyframes dots {
  0% {
    content: "";
  }
  25% {
    content: ".";
  }
  50% {
    content: "..";
  }
  75%,
  100% {
    content: "...";
  }
}

.stage-status {
  border-top: 1px solid var(--line);
}

.stat {
  display: flex;
  align-items: baseline;
  gap: 7px;
}

.stat strong {
  font-weight: 500;
  font-variant-numeric: tabular-nums;
}

#status {
  margin: 0 0 0 auto;
  color: var(--muted);
  font-size: 11px;
  text-align: right;
}

/* write-up */

.about {
  max-width: 76ch;
  padding: 46px 22px 64px;
  margin: 0 auto;
  border-top: 1px solid var(--line);
  font-size: 14px;
  line-height: 1.75;
  color: var(--muted);
}

.about h2 {
  margin: 38px 0 14px;
  color: var(--ink);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.about h2:first-child {
  margin-top: 0;
}

.about p,
.about li {
  margin: 0 0 14px;
}

.about ul {
  margin: 0 0 14px;
  padding-left: 20px;
}

.about li::marker {
  color: var(--accent-dim);
}

.about strong {
  color: var(--ink);
  font-weight: 500;
}

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

.noscript {
  margin: 14px;
}

[hidden] {
  display: none !important;
}

@media (max-width: 820px) {
  main {
    grid-template-rows: auto auto;
  }

  .layout {
    grid-template-columns: minmax(0, 1fr);
  }

  .rail {
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .keys {
    display: none;
  }

  .stage {
    min-height: 70dvh;
  }

  .stage-status {
    flex-wrap: wrap;
  }

  #status {
    width: 100%;
    margin: 0;
    text-align: left;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}