html, body {
  background-color: #383838;
  margin: 0;
  padding: 0;
}
body {
  align-items: center;
  justify-content: center;
  overflow: hidden;
}
canvas {
  box-shadow: 0px 0px 20px 0px rgba(0,0,0,0.5);
  border: none;
  box-sizing: border-box;
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  padding: 0;
  max-height: 100%;
  max-width: 100%;
  touch-action: none;
  vertical-align: middle;
}