html, body {
  height: 100%;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #111;
  font-family: Helvetica, Verdana, sans-serif;
}

canvas#game {
  background: black;
  border: 5px solid white;
  display: block;
  outline: none;
}