:root {
  --bg: #0f172a;
  --panel: #111827;
  --text: #e5e7eb;
  --accent: #22c55e;
  --board: #065f46;
  --cell: #064e3b;
  --cell-alt: #075e47;
  --hint: rgba(255,255,255,0.15);
  --black: #111827;
  --white: #e5e7eb;
}
* { box-sizing: border-box }
html, body { height: 100% }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, Apple Color Emoji, Segoe UI Emoji;
}
.app { max-width: 1100px; margin: 0 auto; padding: 16px }
.header { display: flex; align-items: center; justify-content: space-between; gap: 16px }
.header h1 { margin: 0; font-size: 24px }
.controls { display: flex; align-items: center; gap: 12px; flex-wrap: wrap }
.group { display: flex; align-items: center; gap: 8px }
select, button, .toggle {
  background: var(--panel);
  color: var(--text);
  border: 1px solid #1f2937;
  border-radius: 8px;
  padding: 8px 10px;
}
button { cursor: pointer }
.main { display: grid; grid-template-columns: 1fr 280px; gap: 16px; margin-top: 16px }
.board-wrap { display: flex; justify-content: center; align-items: center }
.board {
  width: min(80vmin, 700px);
  height: min(80vmin, 700px);
  background: var(--board);
  border-radius: 12px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.35);
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
  gap: 3px;
  padding: 3px;
}
.cell {
  background: var(--cell);
  border-radius: 8px;
  position: relative;
}
.cell:nth-child(odd) { background: var(--cell-alt) }
.cell[aria-disabled="true"] { pointer-events: none }
.disc {
  position: absolute;
  inset: 12%;
  border-radius: 50%;
  transform: scale(0.9);
  transition: transform 180ms ease, background 180ms ease, box-shadow 180ms ease;
  box-shadow: inset 0 10px 16px rgba(255,255,255,0.15), inset 0 -10px 16px rgba(0,0,0,0.25);
}
.disc.black { background: var(--black) }
.disc.white { background: var(--white) }
.disc.flip { transform: scale(1) }
.hint { position: absolute; inset: 40%; border-radius: 50%; background: var(--hint) }
.highlight { outline: 2px solid var(--accent) }
.sidebar { background: var(--panel); border-radius: 12px; padding: 12px }
.status .row { display: flex; justify-content: space-between; margin: 6px 0 }
.history h2 { font-size: 16px; margin: 10px 0 }
.history ol { margin: 0; padding-left: 18px; max-height: 50vh; overflow: auto }
.recent h2 { font-size: 16px; margin: 10px 0 }
.recent ul { margin: 0; padding-left: 18px; max-height: 40vh; overflow: auto; list-style: disc }
.recent li { margin: 4px 0; opacity: 0.9 }
@media (max-width: 900px) {
  .main { grid-template-columns: 1fr }
  .sidebar { order: -1 }
}