.demo{position:relative}.demo .editor{height:400px;margin-top:1rem;border:1px solid #666;width:100%}.demo canvas{display:block;margin:0 auto;margin-top:1rem;margin-bottom:1rem;background:#99b199}.run-button{position:absolute;width:100px;top:5px;right:15px;z-index:9999}