:root {
  --bg: #f0ede6;
  --panel: #fbfaf7;
  --ink: #232019;
  --soft: #6d675c;
  --line: #d8d2c6;
  --grid-line: #b7afa0;
  --thick: #6b6456;
  --accent: #9a5b2e;
  --accent-soft: #ecdfd0;
  --given: #232019;
  --user: #9a5b2e;
  --sel: #f3e6d4;
  --peer: #f6f1e9;
  --same: #e9ddca;
  --err: #b23b3b;
  --sans: "Avenir Next", -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #17150f;
    --panel: #1f1c15;
    --ink: #e8e3d8;
    --soft: #9c968a;
    --line: #322e25;
    --thick: #5b5446;
    --accent: #d69a63;
    --accent-soft: #33291d;
    --given: #e8e3d8;
    --user: #d69a63;
    --sel: #3a2f20;
    --peer: #241f17;
    --same: #322a1d;
    --err: #e07070;
  }
}
* { box-sizing: border-box; }
html, body { margin: 0; background: var(--bg); color: var(--ink); }
body { font: 17px/1.55 var(--sans); -webkit-text-size-adjust: 100%; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.wrap { max-width: 640px; margin: 0 auto; padding: 0 20px; }

.top .wrap { display: flex; justify-content: space-between; align-items: center; padding: 18px 20px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; font-size: 19px; letter-spacing: -0.01em; color: var(--ink); text-decoration: none; }
.brand svg { width: 26px; height: 26px; }

.head { padding: 26px 0 10px; text-align: center; }
.head h1 { font-size: clamp(26px, 5vw, 34px); letter-spacing: -0.02em; margin: 0 0 4px; }
.head p { color: var(--soft); margin: 0; font-size: 15px; }

.bar { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin: 18px 0 12px; flex-wrap: wrap; }
.levels { display: flex; gap: 6px; }
.levels button { border: 1px solid var(--line); background: var(--panel); color: var(--soft); border-radius: 999px; padding: 6px 14px; font: inherit; font-size: 14px; cursor: pointer; }
.levels button[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: #fff; }
@media (prefers-color-scheme: dark){ .levels button[aria-pressed="true"]{ color:#151109; } }
.meta { display: flex; gap: 16px; color: var(--soft); font-size: 14px; font-variant-numeric: tabular-nums; }
.meta b { color: var(--ink); font-weight: 600; }

.board { width: 100%; aspect-ratio: 1; background: var(--thick); border: 2px solid var(--thick); border-radius: 8px; overflow: hidden; display: grid; grid-template-columns: repeat(9, 1fr); gap: 1px; touch-action: manipulation; }
.cell { background: var(--panel); display: grid; place-items: center; font-size: clamp(20px, 6vw, 30px); cursor: pointer; user-select: none; position: relative; font-variant-numeric: tabular-nums; }
.cell.r3 { margin-bottom: 1px; } /* visual separators via gaps below */
.board .cell:nth-child(9n+4), .board .cell:nth-child(9n+7) { box-shadow: inset 2px 0 0 var(--thick); }
.row-sep { box-shadow: inset 0 2px 0 var(--thick); }
.cell.given { color: var(--given); font-weight: 600; }
.cell.user { color: var(--user); }
.cell.sel { background: var(--sel); }
.cell.peer { background: var(--peer); }
.cell.same { background: var(--same); }
.cell.err { color: var(--err); }
.cell .marks { position: absolute; inset: 4px; display: grid; grid-template-columns: repeat(3,1fr); grid-template-rows: repeat(3,1fr); font-size: 9px; color: var(--soft); line-height: 1; }
.cell .marks span { display: grid; place-items: center; }

.pad { display: grid; grid-template-columns: repeat(9, 1fr); gap: 6px; margin: 14px 0 8px; }
.pad button { aspect-ratio: 1; border: 1px solid var(--line); background: var(--panel); color: var(--ink); border-radius: 8px; font: inherit; font-size: clamp(18px,5vw,24px); cursor: pointer; }
.pad button:hover { border-color: var(--accent); }
.pad button .rem { display:block; font-size: 11px; color: var(--soft); }

.actions { display: flex; gap: 8px; justify-content: center; flex-wrap: wrap; margin-bottom: 8px; }
.actions button { border: 1px solid var(--line); background: var(--panel); color: var(--ink); border-radius: 8px; padding: 9px 16px; font: inherit; font-size: 15px; cursor: pointer; }
.actions button:hover { border-color: var(--accent); }
.actions button.on { background: var(--accent-soft); border-color: var(--accent); }
.actions .primary { background: var(--accent); border-color: var(--accent); color: #fff; }
@media (prefers-color-scheme: dark){ .actions .primary{ color:#151109; } }

.msg { text-align: center; min-height: 24px; color: var(--accent); font-weight: 600; margin: 6px 0 0; }

.how { color: var(--soft); font-size: 14px; margin: 26px 0 10px; }
.how summary { cursor: pointer; color: var(--ink); }
.how p { margin: 10px 0 0; }

.foot { border-top: 1px solid var(--line); color: var(--soft); font-size: 13px; margin-top: 30px; }
.foot .wrap { padding: 18px 20px 26px; text-align: center; }

@media (max-width: 480px) {
  .pad { gap: 4px; }
  .pad button .rem { display: none; }
}