:root {
  --bg: #0f172a;
  --surface: #1e293b;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --x: #38bdf8;
  --o: #f472b6;
  --win: #facc15;
  color-scheme: dark;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

main {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
  padding: 1.5rem;
}

h1 { margin: 0; letter-spacing: 0.05em; }

.status { margin: 0; min-height: 1.5em; font-size: 1.2rem; color: var(--muted); }

.board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
  width: min(90vw, 360px);
  aspect-ratio: 1;
}

.cell {
  border: none;
  border-radius: 0.75rem;
  background: var(--surface);
  color: var(--text);
  font-size: clamp(2.5rem, 12vw, 4.5rem);
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.1s, background 0.2s;
}

.cell:not(:disabled):hover { background: #334155; }
.cell:focus-visible { outline: 3px solid var(--x); outline-offset: 2px; }
.cell:disabled { cursor: default; }
.cell[data-mark="X"] { color: var(--x); }
.cell[data-mark="O"] { color: var(--o); }
.cell.win { color: var(--bg); background: var(--win); transform: scale(1.04); }

.reset {
  padding: 0.6rem 1.5rem;
  border: 2px solid var(--muted);
  border-radius: 999px;
  background: transparent;
  color: var(--text);
  font-size: 1rem;
  cursor: pointer;
}

.reset:hover { border-color: var(--text); }

.score { display: flex; gap: 2rem; margin: 0; text-align: center; }
.score dt { color: var(--muted); font-size: 0.85rem; }
.score dd { margin: 0; font-size: 1.5rem; font-weight: 700; }