anchor.diff:      }
     }
   
  -  void run() {
  -    window.animationFrame.then(update);
  +  Future run() async {
  +    update(await window.animationFrame);
     }
   
     void update(num delta) {
  
positive.code: import 'dart:html';
  import 'dart:math';
  import 'dart:collection';
  
negative.code: 
    Keyboard() {
      window.onKeyDown.listen((KeyboardEvent event) {
        _keys.putIfAbsent(event.keyCode, () => event.timeStamp);
      });
  
      window.onKeyUp.listen((KeyboardEvent event) {
  