.html, body {
  margin: 0;
  
  padding: 0;
  height: 100%;
  overflow: hidden; /* prevent scrollbars */
  background: red; /* fallback background */
}

#game {
  width: 100%;
  height: auto;
  max-width: 1200px; /* prevent it from stretching too much */
  display: block;
  margin: 0 auto;
}