:root {
  --bg: #0a1118;
  --panel: rgba(18, 26, 36, 0.72);
  --text: #eef2ff;
  --muted: rgba(238, 242, 255, 0.7);
  --border: rgba(238, 242, 255, 0.16);
  --accent: #f59e0b;
  --danger: #f87171;
  --cell: rgba(255,255,255,0.08);
  --light: #f5e7cf;
  --dark: #8a5a35;
  --frame: #2a1a10;
  --shadow: 0 28px 70px rgba(4, 7, 14, 0.5);
  --font-display: "Copperplate", "Palatino Linotype", "Book Antiqua", serif;
  --font-body: "Optima", "Candara", "Segoe UI", sans-serif;
}

[data-theme="light"] {
  --bg: #f5f1ea;
  --panel: rgba(255, 255, 255, 0.84);
  --text: #0f172a;
  --muted: rgba(15, 23, 42, 0.7);
  --border: rgba(15, 23, 42, 0.14);
  --accent: #d97706;
  --danger: #e11d48;
  --cell: rgba(15, 23, 42, 0.05);
  --light: #fff4df;
  --dark: #b07a45;
  --frame: #5b3a21;
  --shadow: 0 20px 45px rgba(15, 23, 42, 0.2);
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: var(--font-body);
  background:
    radial-gradient(900px 600px at 10% 10%, rgba(245, 158, 11, 0.16), transparent 60%),
    radial-gradient(900px 600px at 80% 18%, rgba(16, 185, 129, 0.12), transparent 60%),
    linear-gradient(160deg, rgba(15, 23, 42, 0.28), transparent 55%),
    var(--bg);
  color: var(--text);
  min-height: 100vh;
  position: relative;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(45deg, rgba(255, 255, 255, 0.05) 25%, transparent 25%),
    linear-gradient(135deg, rgba(255, 255, 255, 0.05) 25%, transparent 25%);
  background-size: 26px 26px;
  opacity: 0.18;
  pointer-events: none;
}

.container { max-width: 1100px; margin: 0 auto; padding: 18px 14px 40px; position: relative; z-index: 1; animation: fadeUp 0.6s ease-out; }

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
  padding: 14px 14px 6px;
}
.title { margin: 0; font-size: 32px; font-family: var(--font-display); letter-spacing: 0.6px; }
.subtitle { margin: 0; color: var(--muted); }
.header-actions { display: flex; gap: 10px; flex-wrap: wrap; }

.btn {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--cell);
  color: var(--text);
  padding: 10px 12px;
  border-radius: 12px;
  cursor: pointer;
  font-weight: 700;
  transition: transform 0.15s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}
.btn.primary { border-color: rgba(245, 158, 11, 0.6); background: rgba(245, 158, 11, 0.16); box-shadow: 0 10px 22px rgba(245, 158, 11, 0.2); }
.btn:disabled { opacity: 0.6; cursor: not-allowed; }
.btn:hover { transform: translateY(-1px); }
.btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.status {
  margin: 10px 14px 0;
  padding: 10px 12px;
  background: linear-gradient(145deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0.02));
  border: 1px solid var(--border);
  border-radius: 14px;
  color: var(--muted);
  box-shadow: var(--shadow);
}
.status strong { color: var(--text); }
.sep { margin: 0 8px; opacity: 0.6; }

.layout {
  margin-top: 14px;
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 14px;
}

.panel {
  padding: 14px;
  background: linear-gradient(140deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0.02));
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow);
}
.panel h2 { margin: 0 0 10px; font-size: 18px; }
.panel ul { margin: 0; padding-left: 18px; color: var(--muted); }

.board-section { display: grid; place-items: center; }
.board {
  width: min(92vw, 640px);
  aspect-ratio: 1 / 1;
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  border: 2px solid rgba(255, 255, 255, 0.08);
  border-radius: 16px;
  overflow: hidden;
  background: linear-gradient(140deg, rgba(59, 35, 20, 0.9), rgba(24, 16, 10, 0.9));
  padding: 10px;
  box-shadow: var(--shadow);
  animation: fadeIn 0.5s ease-out;
}

.square {
  position: relative;
  display: grid;
  place-items: center;
  font-size: clamp(22px, 4.8vw, 44px);
  user-select: none;
  cursor: pointer;
  transition: transform 0.15s ease, filter 0.2s ease;
}

.square.light { background: var(--light); }
.square.dark { background: var(--dark); }

[data-theme="light"] .square.light { background: var(--light); }
[data-theme="light"] .square.dark { background: var(--dark); }

.square.selected { outline: 3px solid rgba(245, 158, 11, 0.7); outline-offset: -3px; }
.square.legal::after {
  content: '';
  width: 28%;
  height: 28%;
  border-radius: 999px;
  background: rgba(52, 211, 153, 0.55);
  position: absolute;
}
.square.capture::after { background: rgba(251,113,133,0.55); }
.square:hover { filter: brightness(1.05); transform: translateY(-1px); }

.coord {
  position: absolute;
  font-size: 11px;
  color: rgba(232, 238, 252, 0.7);
  left: 6px;
  bottom: 4px;
}

[data-theme="light"] .coord { color: rgba(15, 23, 42, 0.7); }

.theme-toggle {
  position: fixed;
  right: 14px;
  bottom: 14px;
  width: 46px;
  height: 46px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  box-shadow: var(--shadow);
}

@media (max-width: 920px) {
  .layout { grid-template-columns: 1fr; }
}

@media (max-width: 420px) {
  .btn { width: 100%; }
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn {
  from { opacity: 0; transform: scale(0.98); }
  to { opacity: 1; transform: scale(1); }
}

@media (prefers-reduced-motion: reduce) {
  .container, .board, .btn, .square { animation: none; transition: none; }
}