It is a very interesting and unique mechanic and I'd love to see more of it, though it was a bit hard to figure out the first time what I was supposed to do. Primarily because I accidentally push the shopping cart through the back wall and had to restart the game. I could also see problems arising from the cart being pushed all the way against the wall and not being able to get behind it to push. Perhaps putting the cart in front of the player instead of behind it would help.