public override void Notify()
{
//Debug.WriteLine(" Grid_Wall_Observer: {0} {1}", this.pSubject.pObjA, this.pSubject.pObjB);
AlienGrid pAlienGrid = (AlienGrid)this.pSubject.pObjA;
// If AlienGrid is not already changing directions
if (!pAlienGrid.GetSwitchXDirection() && !pAlienGrid.IsDirectionChangePending())
{
// Tell AlienGrid to move down and change directions
pAlienGrid.SetSwitchXDirection(true);
}
}