Objects overlapping each other when they are crammed in between 2 walls, help!

So Im making this game and I gave a box made of walls and you drag shapes into this box but if you cram a bunch of them in there they start to overlap each other how do you make it so that they just overpower the wall instead of overlapping each other?
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http://gamesalad.com/forums/topic.php?id=27847&replies=1#post-208439
I've added a video to help show the problem incase the are fundamentally the same.