:root {
  --bg: #0e0f12;
  --fg: #e8e9ec;
  --muted: #8a8f99;
  --line: #24262c;
  --accent: #c2a06a;
  --x-color: #6aa9ff;
  --o-color: #ff8a6a;
  --active: #c2a06a33;
  --heat: 192, 160, 106;     /* RGB for accent (heatmap fills) */
  --won-x: #1a2740;
  --won-o: #2c1c18;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--fg);
  font-size: 15px;
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  justify-content: center;
}
main {
  width: 100%;
  max-width: 1080px;
  padding: 32px 24px 48px;
}
header { margin-bottom: 24px; }
h1 {
  font-size: 32px;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin: 0 0 4px;
}
.subtitle { color: var(--muted); margin: 0; }

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 32px;
  align-items: start;
}
@media (max-width: 820px) {
  .layout { grid-template-columns: 1fr; }
}

/* ---------------- Board ---------------- */

.board-wrap { display: flex; flex-direction: column; gap: 12px; }
.board {
  aspect-ratio: 1 / 1;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 6px;
  padding: 6px;
  background: var(--line);
  border-radius: 10px;
  user-select: none;
}
.subboard {
  position: relative;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 2px;
  background: var(--bg);
  border-radius: 6px;
  padding: 4px;
  border: 1.5px solid transparent;
  transition: border-color 120ms ease, background 120ms ease;
}
.subboard.active { border-color: var(--accent); background: var(--active); }
.subboard.won-x { background: var(--won-x); }
.subboard.won-o { background: var(--won-o); }
.subboard.drawn { opacity: 0.5; }

.subboard .overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(48px, 8vw, 92px);
  font-weight: 700;
  pointer-events: none;
  opacity: 0.18;
}
.subboard.won-x .overlay { color: var(--x-color); }
.subboard.won-o .overlay { color: var(--o-color); }

.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(14px, 2.4vw, 24px);
  font-weight: 600;
  background: #15171b;
  border-radius: 3px;
  cursor: pointer;
  transition: background 100ms ease;
  position: relative;
}
.cell:hover:not(.disabled):not(.x):not(.o) { background: #1d2026; }
.cell.disabled { cursor: not-allowed; }
.cell.x { color: var(--x-color); }
.cell.o { color: var(--o-color); }
.cell.last-move { box-shadow: inset 0 0 0 2px var(--accent); }
.cell.heat::before {
  content: "";
  position: absolute;
  inset: 0;
  background: rgba(var(--heat), var(--heat-alpha, 0));
  border-radius: inherit;
  pointer-events: none;
}

/* ---------------- Panel ---------------- */

.panel {
  display: flex;
  flex-direction: column;
  gap: 14px;
  background: #14151a;
  padding: 18px;
  border-radius: 10px;
  border: 1px solid var(--line);
}
.panel-row { display: flex; flex-direction: column; gap: 6px; }
.panel-row label { color: var(--muted); font-size: 13px; }
select, input[type=range] {
  width: 100%;
  background: #0e0f12;
  color: var(--fg);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 6px 8px;
  font: inherit;
}
input[type=range] { padding: 0; }
.check { display: flex; align-items: center; gap: 8px; cursor: pointer; }
.check input { accent-color: var(--accent); }

.seg { display: flex; gap: 4px; background: #0e0f12; border: 1px solid var(--line); border-radius: 6px; padding: 3px; }
.seg button {
  flex: 1;
  padding: 6px 8px;
  background: transparent;
  border: none;
  color: var(--muted);
  font: inherit;
  border-radius: 4px;
  cursor: pointer;
}
.seg button.active { background: var(--line); color: var(--fg); }

.primary {
  padding: 10px 14px;
  background: var(--accent);
  color: #1a1409;
  border: none;
  border-radius: 6px;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
}
.primary:hover { filter: brightness(1.05); }
.primary:disabled { opacity: 0.5; cursor: not-allowed; }

.status {
  text-align: center;
  color: var(--fg);
  font-weight: 500;
  min-height: 1.4em;
}
.status.thinking { color: var(--accent); }
.status.error { color: #ff6a6a; }
.status.win { color: var(--x-color); }
.status.loss { color: var(--o-color); }
.status.draw { color: var(--muted); }

/* ---------------- Introspection ---------------- */

.introspect h3 {
  margin: 6px 0 8px;
  font-size: 13px;
  font-weight: 500;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.value-label {
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--muted);
  margin-bottom: 4px;
}
.value-label span:nth-child(2) { color: var(--fg); font-variant-numeric: tabular-nums; }
.value-bar {
  position: relative;
  height: 6px;
  background: #0e0f12;
  border-radius: 3px;
  overflow: hidden;
}
.value-bar::before {
  content: "";
  position: absolute;
  left: 50%; top: 0; bottom: 0;
  width: 1px;
  background: var(--line);
}
#value-fill {
  position: absolute;
  top: 0; bottom: 0;
  background: var(--accent);
  transition: left 200ms ease, width 200ms ease;
}
#top-moves {
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
  font-variant-numeric: tabular-nums;
  font-size: 13px;
  color: var(--muted);
}
#top-moves li {
  display: grid;
  grid-template-columns: 1fr auto auto;
  gap: 12px;
  padding: 4px 0;
}
#top-moves li .move-label { color: var(--fg); }
.elapsed {
  margin-top: 10px;
  font-size: 12px;
  color: var(--muted);
  text-align: right;
}

footer {
  margin-top: 32px;
  text-align: center;
  color: var(--muted);
  font-size: 12px;
}