Nice idea, the physics work nicely, center-mechanic is weel put together.
But to be honest I don't really see how it can be made much more interesting, I think it loose quite a bit of its novelty when the levels just get spikingly harder, from doing nothing to feeling like you can't do anything.
It's nonetheless impressive to have achieve that much in 4 hours, but I would have love to see a bit more, and not just difficulty-wise.