anchor.diff:  
     void _drawPop(dartlib.Coordinate start, List<dartlib.Coordinate> reveals) {
       assert(reveals.length > 0);
  -    const animationOffset = const dartlib.Vector(-88, -88);
       final distances = dartlib.$(reveals).select((r) =>
           new dartlib.Tuple<num, dartlib.Coordinate>((start - r).length, r))
           .toList();
  
positive.code: 
      for(final t in distances) {
        final c = t.Item2;
        final squareOffset = animationOffset +
            new dartlib.Vector(SquareElement._size * c.x, SquareElement._size * c.y);
  
        final delay = ((t.Item1 - closest) * frameScale).toInt();
  
        // start a fake animation
        _animationLayer.add(new TextAniRequest('balloon_pop', 29, squareOffset, delay));
      }
    }
  
  
negative.code:   static const _backgroundSize = const dartlib.Size(2048, 1536);
    static const _backgroundHoleSize = 16 * SquareElement._size + 2 * _edgeOffset;
    static const _boardOffset = const dartlib.Vector(352, 96);
    static const _popExplodeAnimationOffset = const dartlib.Vector(-88, -88);
  
  
    final TextureAnimationElement _animationLayer;
    final bool _targetMode;
  