Gravity Pinball

I'm still writing my final thesis and still creating some concepts for interactive astronomy stuff. Today I tested an idea I've had for some time, just to see if it would work. I've been wanting to include some kind of a pinball machine that would use small gravity fields to guide the ball. I build a very crude version this morning out of plastic wrap and push pins, but it actually worked surprisingly well when I rolled small wooden pearls along the wrap. Einstein's theory of relativity, anyone?