html, body {
  width: 100%;
  height: 100%;
  padding: 0;margin: 0;
  background-color: #3a3a3a;
}

body {
  padding: 0;margin: 0;
  overflow: hidden;
}

canvas {
  max-width: 100%; 
  max-height: 100%;
  
  transform: translateY(50%);
  margin: auto; 
  overflow: auto; 
  position: fixed; 
  object-fit: contain; 
  top: 50%;
  -ms-transform: translateY(-50%);
  transform: translateY(-50%);
  
  display: block;
  margin: 0 auto;
  padding: 0;
}