* { margin: 0; padding: 0; box-sizing: border-box; }
html, body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background: #000;
}
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", monospace;
  user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
  touch-action: none;
}
canvas#game {
  display: block;
  cursor: crosshair;
}