html, body {
  margin: 0;
  padding: 0;
  background: #000;
  height: 100%;
  overflow: hidden;
  overscroll-behavior: none;
  position: fixed;
  width: 100%;
  font-family: "Courier New", monospace;
}

/* center the fixed-aspect play area; the body's black shows as letterbox bars */
body {
  display: flex;
  align-items: center;
  justify-content: center;
}

#game {
  display: block;
  background: #000;
  touch-action: none;
  -webkit-user-select: none;
  user-select: none;
  -webkit-touch-callout: none;
}

/* touch devices held in portrait: ask for landscape instead of a tiny letterbox */
#rotate {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 10;
  background: #000;
  color: #e0e0e0;
  font-size: 22px;
  line-height: 1.6;
  text-align: center;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

@media (orientation: portrait) and (pointer: coarse) {
  #rotate { display: flex; }
}