html, body {  
    text-align: center;  
    background-color: #FFFFFF; 
    margin: auto;
    padding: 10px;
}  
canvas {
  margin: 10px auto;
  width:100%;
  display: block;
  border: solid 13px black;
  padding: 26px 26px;
  box-shadow: -6px 6px 6px gray;
}