I like the concept, and in a fully-fleshed out game I'd love there to be an increase of difficulty. Just figuring what the things are and what to do with them is hard enough without having them also happening on the other side of the screen at the same time. Would definitely like to see it ramp up. First, with things alternating between halves of the screen so you can get a handle on what you're supposed to be doing on each side, then you can have things happening all at once.