html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background: #111;
}

canvas {
  display: block;
  background: #222;
}

#rulebar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: rgba(0,0,0,0.75);
  color: white;
  font-family: sans-serif;
  font-size: 14px;
  text-align: center;
  padding: 4px;
  pointer-events: none;
}