Retrobooster has its first playable demo for Windows and Linux. The full game is about two-thirds through development, so the demo will be improved as the game becomes more complete. Fortunately, Indie DB has really fast servers so you can download the demo here a lot faster than from my own webserver.
Visit the Retrobooster forum if you want to discuss the demo. I'm really interested in getting some feedback to help make it a better game.