I thought I wasn't gonna be able to figure something out for the Newgrounds comp, but it turns out I had a bit of an idea. It's yet another Breakout clone, but with the 'endless game' style. So far, there's no music, three power-ups, and the collision's a bit janky, but it's getting there.
Also, the assets are entirely open-source, found on Opengameart.org.
<img src="https://dl.dropboxusercontent.com/u/919275/Block%20Tower%20Breakdown/Screenshot.png" border="0">
Play the game here.
I'll probably upload the full game up onto the arcade later once it's more feature-complete, and update it as I go, and then I'll submit it to Newgrounds once I'm satisfied.