html, body {
  margin: 0;
  padding: 0;
}
canvas {
    display: block;
    width: 100%;
    height: 100%;
    margin: auto;
    border: solid 13px black;
    padding: 10px 10px;
    box-shadow: -6px 6px 6px gray;
    overflow: auto;
    position: fixed;
    object-fit: contain;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}