:root {
  --bg: #0e1116;
  --panel: #161b22;
  --panel-2: #1c2230;
  --text: #e6edf3;
  --muted: #8b96a7;
  --accent: #7ee787;
  --accent-2: #79c0ff;
  --border: #2a313c;
  --chip: #21262d;
  --chip-hover: #2d333b;
  --danger: #ff7b72;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  font-size: 15px;
  line-height: 1.55;
}

header {
  text-align: center;
  padding: 38px 20px 20px;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, #11161d, var(--bg));
}

header h1 {
  margin: 0;
  font-size: 28px;
  letter-spacing: -0.01em;
}

header .sub {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 14px;
}

main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 22px 20px 60px;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px 18px;
  margin-bottom: 14px;
}

.rule-row {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.rule-row label {
  font-weight: 600;
  margin-right: 4px;
}

#rule {
  width: 90px;
  font-size: 20px;
  font-weight: 600;
  text-align: center;
  padding: 6px 8px;
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
}

.step {
  width: 30px;
  height: 30px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--chip);
  color: var(--text);
  font-size: 18px;
  line-height: 1;
  cursor: pointer;
}
.step:hover { background: var(--chip-hover); }

.binary {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color: var(--accent);
  font-size: 16px;
  margin-left: 6px;
  letter-spacing: 0.12em;
}

.famous {
  margin-top: 12px;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  align-items: center;
}

.famous-label {
  color: var(--muted);
  font-size: 13px;
  margin-right: 4px;
}

.chip {
  background: var(--chip);
  color: var(--text);
  border: 1px solid var(--border);
  padding: 5px 10px;
  border-radius: 999px;
  cursor: pointer;
  font-size: 13px;
}
.chip em {
  color: var(--muted);
  font-style: normal;
  margin-left: 4px;
  font-size: 12px;
}
.chip:hover { background: var(--chip-hover); border-color: #3a4250; }

.diagram {
  margin-top: 16px;
  display: grid;
  grid-template-columns: repeat(8, minmax(0, 1fr));
  gap: 8px;
}

.dcell {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  background: var(--panel-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 4px 6px;
}
.dcell .top, .dcell .bot {
  display: flex;
  gap: 2px;
}
.dcell .box {
  width: 14px;
  height: 14px;
  border: 1px solid #3a4250;
  border-radius: 2px;
}
.dcell .box.on { background: var(--text); border-color: var(--text); }
.dcell .box.off { background: transparent; }
.dcell.firing {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px var(--accent), 0 0 16px rgba(126, 231, 135, 0.45);
  background: #1f2a23;
  transition: box-shadow 80ms ease-out;
}
.dcell.firing .label { color: var(--accent); }
.dcell .label {
  font-family: ui-monospace, monospace;
  color: var(--muted);
  font-size: 11px;
  margin-top: 2px;
}

.controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 14px;
  align-items: end;
}

.ctrl {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.ctrl label {
  color: var(--muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.ctrl input[type="number"],
.ctrl select {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 8px;
  font-size: 14px;
}
.ctrl input[type="range"] {
  width: 100%;
}
.rangeVal {
  color: var(--accent-2);
  font-family: ui-monospace, monospace;
  font-size: 12px;
}

.ctrl.btns {
  flex-direction: row;
  gap: 6px;
  flex-wrap: wrap;
}
.ctrl.btns button {
  background: var(--chip);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 13px;
  cursor: pointer;
}
.ctrl.btns button:hover { background: var(--chip-hover); }
.ctrl.btns button.primary {
  background: var(--accent);
  color: #0a0f14;
  border-color: var(--accent);
  font-weight: 600;
}
.ctrl.btns button.primary:hover { filter: brightness(1.05); }

.stepper-row {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: center;
  justify-content: space-between;
}
.stepper-btns {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.stepper-btns button {
  background: var(--chip);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 13px;
  cursor: pointer;
}
.stepper-btns button:hover { background: var(--chip-hover); }
.stepper-btns button.primary {
  background: var(--accent);
  color: #0a0f14;
  border-color: var(--accent);
  font-weight: 600;
}
.stepper-btns button.primary:hover { filter: brightness(1.05); }
.stepper-btns button:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}
.stepper-speed {
  display: flex;
  align-items: center;
  gap: 8px;
  min-width: 220px;
}
.stepper-speed label {
  color: var(--muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.stepper-speed input[type="range"] { flex: 1; }
.stepper-status {
  margin-top: 12px;
  color: var(--muted);
  font-size: 13px;
  font-family: ui-monospace, monospace;
  background: var(--panel-2);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 12px;
}
.stepper-status strong { color: var(--accent-2); font-weight: 600; }
.stepper-status .fire {
  color: var(--accent);
  font-weight: 600;
}

.canvas-wrap {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  margin-bottom: 18px;
  overflow: auto;
  display: flex;
  justify-content: center;
}

.canvas-stack {
  position: relative;
  display: inline-block;
  line-height: 0;
}

.canvas-stack canvas {
  display: block;
  image-rendering: pixelated;
  image-rendering: crisp-edges;
  border-radius: 4px;
}

#canvas {
  background: #000;
}

#overlay {
  position: absolute;
  top: 0;
  left: 0;
  pointer-events: none;
  background: transparent;
}

.about {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px 24px;
}
.about h2 {
  margin: 18px 0 8px;
  font-size: 18px;
  color: var(--accent-2);
}
.about h2:first-child { margin-top: 4px; }
.about p { color: #d0d7de; }
.about a { color: var(--accent-2); text-decoration: none; }
.about a:hover { text-decoration: underline; }
.about code {
  background: var(--panel-2);
  padding: 1px 6px;
  border-radius: 4px;
  font-family: ui-monospace, monospace;
  font-size: 13px;
  color: var(--accent);
}
.about ul { padding-left: 22px; }
.about li { margin-bottom: 6px; }

footer {
  text-align: center;
  color: var(--muted);
  font-size: 12px;
  padding: 20px;
  border-top: 1px solid var(--border);
}

@media (max-width: 700px) {
  .diagram { grid-template-columns: repeat(4, 1fr); }
  header h1 { font-size: 22px; }
}