:root {
  color-scheme: light;
  --paper: #f4efe4;
  --card: #fffdf8;
  --ink: #24211d;
  --muted: #746d63;
  --line: #aaa196;
  --line-strong: #4a443d;
  --paired: #e8e1d5;
  --selected: #dcecff;
  --button: #2f2b26;
}

* { box-sizing: border-box; }
html { color-scheme: light only; -webkit-text-size-adjust: 100%; }
body {
  margin: 0; min-height: 100vh;
  background: radial-gradient(circle at top, rgba(255,255,255,.72), transparent 34rem), var(--paper);
  color: var(--ink); font-family: Georgia, "Times New Roman", serif;
}
button { font: inherit; -webkit-tap-highlight-color: transparent; }
.app-shell {
  width: min(96vw, 650px); margin: 0 auto;
  padding: max(20px, env(safe-area-inset-top)) 0 max(28px, env(safe-area-inset-bottom));
}
.topbar { display: flex; align-items: flex-end; justify-content: space-between; gap: 16px; margin: 0 1vw 18px; }
h1 { margin: 0; font-size: clamp(2rem, 7vw, 3.2rem); line-height: .95; letter-spacing: -.04em; }
.subtitle { margin: 10px 0 0; color: var(--muted); font: .94rem/1.4 system-ui, sans-serif; }
.difficulty {
  flex: 0 0 auto; padding: 7px 10px; border: 1px solid var(--line); border-radius: 999px;
  color: var(--muted); background: rgba(255,255,255,.35); font: 700 .76rem system-ui, sans-serif;
}
.game-card {
  padding: clamp(14px, 3vw, 24px); border: 1px solid rgba(70,62,52,.18); border-radius: 18px;
  background: rgba(255,253,248,.8); box-shadow: 0 16px 50px rgba(68,57,43,.08);
}
.board {
  --cell: min(10.7vw, 58px);
  display: grid; grid-template-columns: repeat(8, var(--cell)); grid-template-rows: repeat(7, var(--cell));
  width: max-content; max-width: 100%; margin: 3px auto 18px;
  border: 2px solid var(--line-strong); background: var(--line);
}
.cell {
  display: grid; place-items: center; width: var(--cell); height: var(--cell);
  border: 1px solid var(--line); background: rgba(255,255,255,.7);
  color: var(--ink); font: 800 clamp(1.2rem, 5vw, 1.9rem) system-ui, sans-serif;
  cursor: pointer; user-select: none; touch-action: manipulation; outline: none;
}
.cell.paired { background: var(--paired); }
.cell.domino-top { border-top: 2px solid var(--line-strong); }
.cell.domino-right { border-right: 2px solid var(--line-strong); }
.cell.domino-bottom { border-bottom: 2px solid var(--line-strong); }
.cell.domino-left { border-left: 2px solid var(--line-strong); }
.cell.selected { position: relative; z-index: 1; background: var(--selected); box-shadow: inset 0 0 0 3px rgba(25,101,160,.3); }
.cell:focus-visible { position: relative; z-index: 2; box-shadow: inset 0 0 0 3px rgba(25,101,160,.35); }
.instruction, .message { text-align: center; font-family: system-ui, sans-serif; }
.instruction { margin: 0; color: var(--muted); font-size: .82rem; }
.message { min-height: 26px; margin: 11px 0 2px; color: var(--muted); font-size: .92rem; font-weight: 650; }
.message.solved { color: #28743a; font-weight: 800; }
.actions { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 10px; }
.action-button {
  min-height: 52px; border-radius: 12px; padding: 10px 14px; font: 800 .95rem system-ui, sans-serif;
  cursor: pointer; touch-action: manipulation;
}
.action-button.primary { border: 1px solid var(--button); background: var(--button); color: var(--card); }
.action-button.secondary { border: 1px solid var(--line-strong); background: transparent; color: var(--ink); }
.action-button.confirming { background: #efe0cf; color: var(--ink); border-color: var(--line-strong); }
.action-button:active { transform: translateY(1px); }
footer { padding: 14px 8px 0; text-align: center; color: var(--muted); font: .78rem system-ui, sans-serif; }

@media (max-width: 430px) {
  .app-shell { width: 99vw; }
  .topbar { align-items: flex-start; }
  .subtitle { max-width: 225px; font-size: .84rem; }
  .difficulty { padding: 6px 8px; font-size: .66rem; }
  .game-card { padding: 11px 5px 15px; border-radius: 14px; }
  .board { --cell: 11.4vw; margin-bottom: 15px; }
  .actions { margin-inline: 5px; gap: 8px; }
  .action-button { min-height: 49px; font-size: .9rem; }
}