anchor.diff:      final List<_HeroQuestState> _newHeroes = <_HeroQuestState>[];
       for (_HeroMatch heroPair in heroes.values) {
         assert(heroPair.from != null || heroPair.to != null);
  +      if ((heroPair.from == null && !heroPair.to.alwaysAnimate) ||
  +          (heroPair.to == null && !heroPair.from.alwaysAnimate))
  +        continue;
         _HeroManifest from = heroPair.from?._takeChild(animationArea);
         assert(heroPair.to == null || heroPair.to is HeroState);
         _HeroManifest to = heroPair.to?._takeChild(animationArea);
  
positive.code: }
  
  abstract class HeroHandle {
    _HeroManifest _takeChild(Rect animationArea);
  }
  
  
negative.code:   final AnimatedRelativeRectValue currentRect;
    final AnimatedValue<double> currentTurns;
  
    bool get alwaysAnimate => true;
  
    bool get taken => _taken;
    bool _taken = false;
    _HeroManifest _takeChild(Rect animationArea) {
  