* { box-sizing: border-box; }
html { overscroll-behavior: none; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: #faf8ef;
  color: #776e65;
  touch-action: manipulation;
  overscroll-behavior: none;
  -webkit-tap-highlight-color: transparent;
  min-height: 100dvh;
}
.container {
  width: min(480px, 100%);
  margin: 0 auto;
  padding: calc(16px + env(safe-area-inset-top)) 16px calc(24px + env(safe-area-inset-bottom));
}
.header { display: flex; justify-content: space-between; align-items: flex-start; gap: 12px; flex-wrap: wrap; }
h1 { margin: 0; font-size: 52px; color: #776e65; line-height: 1; }
.tagline { margin: 8px 0 0; font-size: 15px; }
.scores { display: flex; gap: 8px; }
.score-box {
  background: #bbada0; color: #fff; border-radius: 6px;
  padding: 8px 14px; text-align: center; min-width: 74px;
}
.score-box span { display: block; font-size: 12px; text-transform: uppercase; opacity: 0.9; }
.score-box strong { font-size: 20px; }
.controls { display: flex; gap: 10px; margin: 18px 0 10px; }
.controls button {
  flex: 1; min-height: 48px;
  background: #8f7a66; color: #fff; border: 0; border-radius: 6px;
  padding: 10px 18px; font-size: 16px; font-weight: 600; cursor: pointer;
}
.dpad button {
  background: #8f7a66; color: #fff; border: 0; border-radius: 10px;
  padding: 10px; font-size: 24px; font-weight: 600; cursor: pointer;
  min-height: 64px; touch-action: manipulation;
}
.controls button:hover, .dpad button:hover { background: #7a6757; }
.message { min-height: 24px; font-weight: 700; text-align: center; margin: 6px 0 12px; }
.message.win { color: #2a7a3b; }
.message.over { color: #b3402a; }
.board {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px;
  background: #bbada0; border-radius: 10px; padding: 10px;
  touch-action: none; user-select: none; -webkit-user-select: none;
}
.cell {
  aspect-ratio: 1; border-radius: 6px; display: flex; align-items: center; justify-content: center;
  font-weight: 800; background: rgba(238, 228, 218, 0.35); color: #776e65;
}
.cell:empty { background: rgba(238, 228, 218, 0.35); }
.cell.tile-2 { background: #eee4da; font-size: clamp(24px, 7vw, 32px); }
.cell.tile-4 { background: #ede0c8; font-size: clamp(24px, 7vw, 32px); }
.cell.tile-8 { background: #f2b179; color: #fff; font-size: clamp(24px, 7vw, 32px); }
.cell.tile-16 { background: #f59563; color: #fff; font-size: clamp(24px, 7vw, 32px); }
.cell.tile-32 { background: #f67c5f; color: #fff; font-size: clamp(24px, 7vw, 32px); }
.cell.tile-64 { background: #f65e3b; color: #fff; font-size: clamp(24px, 7vw, 32px); }
.cell.tile-128 { background: #edcf72; color: #fff; font-size: clamp(20px, 6vw, 26px); }
.cell.tile-256 { background: #edcc61; color: #fff; font-size: clamp(20px, 6vw, 26px); }
.cell.tile-512 { background: #edc850; color: #fff; font-size: clamp(20px, 6vw, 26px); }
.cell.tile-1024 { background: #edc53f; color: #fff; font-size: clamp(17px, 5vw, 22px); }
.cell.tile-2048 { background: #edc22e; color: #fff; font-size: clamp(17px, 5vw, 22px); }
.cell.tile-super { background: #3c3a32; color: #fff; font-size: clamp(15px, 4.5vw, 20px); }
.help { font-size: 14px; line-height: 1.5; }
.dpad {
  display: grid; grid-template-columns: repeat(3, 64px); gap: 8px;
  justify-content: center; margin-top: 16px;
}
/* On a desktop with a mouse/keyboard, the keys are enough — hide the pad. */
@media (hover: hover) and (pointer: fine) {
  .dpad { display: none; }
}
.dpad button:nth-child(1) { grid-column: 2; }
.dpad button:nth-child(2) { grid-column: 1; grid-row: 2; }
.dpad button:nth-child(3) { grid-column: 2; grid-row: 2; }
.dpad button:nth-child(4) { grid-column: 3; grid-row: 2; }
@media (max-width: 480px) {
  h1 { font-size: 40px; }
  .container { padding-left: 12px; padding-right: 12px; }
  .board { gap: 8px; padding: 8px; }
  .score-box { min-width: 64px; padding: 6px 10px; }
  .help { font-size: 13px; }
}