html, body {
  margin: 0;
  padding: 0;
  background-color: black;
  -webkit-transition: background-color 0.2s ease-out;
  -moz-transition: background-color 0.2s ease-out;
  -o-transition: background-color 0.2s ease-out;
  transition: background-color 0.2s ease-out;
}
canvas { 
  max-width: 100%; 
  max-height: 100%; 
  margin: auto; 
  overflow: auto; 
  position: fixed; 
  object-fit: contain; 
  top: 0; 
  bottom: 0; 
  left: 0; 
  right: 0; 
}