anchor.diff:      );
       final joint = _FlipperJoint(jointDef);
       world.createJoint(joint);
  -    unawaited(mounted.whenComplete(joint.unlock));
     }
   
     List<FixtureDef> _createFixtureDefs() {
  
positive.code: 
      return body;
    }
  }
  
  class _FlipperSpriteComponent extends SpriteComponent with HasGameRef {
  
negative.code:   /// The joint is locked when initialized in order to force the [Flipper]
    /// at its resting position.
    void lock() {
      final angle = _halfSweepingAngle * side.direction;
      setLimits(angle, angle);
    }
  
    /// Unlocks the [Flipper] from its resting position.
  