anchor.diff:      _checkEnableGravity();
   
       _checkSpeedLimits();
  +
  +    if(_checker != null) _checker();
   
       speedX += _accelerationDirection * accelerationX * time;
       speedY += _accelerationDirection * accelerationY * time;
  
positive.code:     y = y + directionSystem.mainDirection.y * distance;
    }
  
    //TODO: stop it if it reaches it's goal
    void moveTo(int x, int y) {
      directionSystem.setMainDirectionFromTo(this.x, this.y, x, y);
    }
  
    /**
  
negative.code:   State _context;
  
    num _accelerationDirection = 0;
  
    Function _checker;
  
    static const int _NO_ACCELERATION_DIRECTION = 0;
  
  