anchor.diff:  
       var div = new DivElement()
                   ..className = 'pexeso-card'
  -                ..append(back)
  -                ..append(front);
  -    container.append(div);
  +                ..children.addAll([back, front]);
  +
  +    container.children.add(div);
   
       return new Card(div, false, id);
     }
  
positive.code:    * Creates the card with DOM given the [backImage] and [frontImage] and
     * appends it to [container].
     */
    factory Card.withDom(Node container, String backImage, String frontImage, id) {
      var back = new ImageElement(src: backImage)
                  ..className = 'back';
      var front = new ImageElement(src: frontImage)
  
negative.code: 
  void main() {
    prepareGame();
  }
  
  void prepareGame() {
  