:root {
  --bg: #0d0f12;
  --fg: #e7e9ea;
  --muted: #9aa0a6;
  --p1: #3da5ff; /* P1色 */
  --p2: #ff5d69; /* P2色 */
  --grid: #8b949e; /* 格子の灰色線 */
  --lineWidth: 4px;
  --cellFillAlpha: 0.18;
  --highlightAlpha: 0.25;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Noto Sans JP", "Apple Color Emoji", "Segoe UI Emoji";
}

header {
  padding: 12px 16px 0;
}

h1 {
  margin: 0 0 8px;
  font-size: 20px;
  letter-spacing: 0.08em;
}

.controls {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 8px;
}

button, select {
  background: #1b1f24;
  color: var(--fg);
  border: 1px solid #2c333a;
  padding: 8px 12px;
  border-radius: 8px;
  cursor: pointer;
}

button:hover, select:hover {
  border-color: #3a424b;
}

.status {
  display: flex;
  gap: 16px;
  align-items: center;
  padding: 8px 0 12px;
  color: var(--muted);
}

#turnInfo {
  color: var(--fg);
  font-weight: 600;
}

main {
  display: grid;
  place-items: center;
  padding: 8px 16px 24px;
}

canvas {
  background: #0f1115;
  border: 1px solid #232a31;
  border-radius: 12px;
  touch-action: manipulation;
}

footer {
  padding: 0 16px 16px;
  color: var(--muted);
  line-height: 1.5;
  max-width: 720px;
  margin: 0 auto;
}