I have a foster kitten who has made a game of flinging as much litter as possible out of the litterbox. he never actually uses it when he does this...just flings it as hard as he can. he's even figured out how to do it with the covered box. how on earth can I stop him doing this? I am tired of having to sweep half to 2/3 of the litterbox off the floor almost every day(no exaggeration).