:root {
  --bg: #fafaf7;
  --fg: #1d1d1b;
  --muted: #7a7a72;
  --line: #c9c9c0;
  --line-strong: #1d1d1b;
  --given: #1d1d1b;
  --entry: #2a5bd7;
  --sel: #bfd4ff;
  --peer: #eceff7;
  --same: #d9e4ff;
  --bad: #fbd5d5;
  --bad-fg: #b3261e;
  --accent: #2a5bd7;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #161618;
    --fg: #ececea;
    --muted: #8d8d86;
    --line: #3a3a3e;
    --line-strong: #c9c9c0;
    --given: #ececea;
    --entry: #8fb0ff;
    --sel: #2f4a8a;
    --peer: #22232a;
    --same: #2a3a66;
    --bad: #4a2224;
    --bad-fg: #ff8a80;
    --accent: #8fb0ff;
  }
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.4 system-ui, sans-serif;
  padding: 0 16px;
}
main { max-width: 520px; margin: 0 auto; padding-block: 16px; }
[x-cloak] { display: none !important; }

header { display: flex; align-items: center; gap: 12px; }
h1 { font-size: 1.25rem; margin: 0; flex: 1; letter-spacing: 0.02em; }
.timer { font-variant-numeric: tabular-nums; font-size: 1.25rem; }
.timer.paused { color: var(--muted); }

button {
  font: inherit;
  color: var(--fg);
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 8px 12px;
  cursor: pointer;
}
button:hover:not(:disabled) { border-color: var(--accent); }
button.on { background: var(--accent); border-color: var(--accent); color: var(--bg); }
button.icon { padding: 4px 10px; font-size: 0.9rem; }
button:disabled, button.off { opacity: 0.3; cursor: default; }

.menu { text-align: center; padding-block: 32px; }
.levels { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.levels button { text-transform: capitalize; padding: 12px 24px; font-size: 1.1rem; }
.stats { color: var(--muted); font-size: 0.9rem; }

.meta { display: flex; justify-content: space-between; text-transform: capitalize; color: var(--muted); padding: 8px 2px; }
.won { color: var(--accent); font-weight: 600; }

.board-wrap { position: relative; }
.board {
  display: grid;
  grid-template-columns: repeat(9, minmax(0, 1fr));
  grid-template-rows: repeat(9, minmax(0, 1fr));
  aspect-ratio: 1;
  border: 2px solid var(--line-strong);
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}
.board.hidden { visibility: hidden; }
.veil {
  position: absolute; inset: 0;
  display: grid; place-items: center;
  background: var(--bg); border: 2px solid var(--line); color: var(--muted);
  cursor: pointer;
}

.cell {
  position: relative;
  display: grid;
  place-items: center;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  cursor: pointer;
}
.cell.edge-r { border-right: 0; }
.cell.edge-b { border-bottom: 0; }
.cell.box-r { border-right: 2px solid var(--line-strong); }
.cell.box-b { border-bottom: 2px solid var(--line-strong); }
.cell.peer { background: var(--peer); }
.cell.same { background: var(--same); }
.cell.selected { background: var(--sel); }
.cell.conflict { background: var(--bad); }

.cell.win { animation: wave 0.7s ease var(--d, 0ms) both; }
@keyframes wave {
  0%, 100% { transform: scale(1); }
  40% { transform: scale(1.25); background: var(--sel); z-index: 1; }
}

.confetti { position: fixed; inset: 0; width: 100%; height: 100%; pointer-events: none; z-index: 10; }

.digit { font-size: clamp(1.2rem, 6vw, 1.9rem); color: var(--entry); }
.cell.given .digit { color: var(--given); font-weight: 600; }
.cell.conflict .digit { color: var(--bad-fg); }

.cands {
  position: absolute; inset: 2px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  font-size: clamp(0.5rem, 2.4vw, 0.75rem);
  color: var(--muted);
  text-align: center;
  line-height: 1;
  place-items: center;
}
.cands .hl { color: var(--accent); font-weight: 700; }

.pad { display: grid; grid-template-columns: repeat(9, 1fr); gap: 6px; margin-top: 16px; }
.pad button { padding: 10px 0; font-size: 1.25rem; }
.tools { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; }
.tools button { flex: 1 1 auto; font-size: 0.9rem; }
.options { display: flex; flex-wrap: wrap; justify-content: center; gap: 8px 24px; margin-top: 16px; }
.options label { display: flex; align-items: center; gap: 8px; cursor: pointer; }
.options input { width: 1.1rem; height: 1.1rem; accent-color: var(--accent); }