* { margin: 0; padding: 0; box-sizing: border-box; }

html, body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background: #70c5ce;
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  -webkit-user-select: none;
  user-select: none;
  touch-action: none;
  -webkit-tap-highlight-color: transparent;
}

#stage { position: fixed; inset: 0; }

#game {
  display: block;
  width: 100%;
  height: 100%;
  cursor: pointer;
}

#mute {
  position: absolute;
  top: 12px;
  right: 14px;
  width: 42px;
  height: 42px;
  border: none;
  border-radius: 11px;
  background: rgba(0, 0, 0, 0.26);
  color: #fff;
  font-size: 20px;
  line-height: 1;
  cursor: pointer;
  z-index: 5;
  transition: background 0.15s ease;
}
#mute:hover { background: rgba(0, 0, 0, 0.42); }
#mute:active { transform: scale(0.94); }