html, body {
  background-color: #181818;
}
canvas {
  padding: 0;
  margin: auto;
  display: block;
  width: 800px;
  height: 600px;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  box-shadow: rgba(0, 0, 0, 0.1) 0px 4px 12px;
}