try the small version, it should be fine. also try the microsoft VM, it does make a difference on small machines.
that slow down problem is not really related to the memory usage, but more because of the way I manage the balls I think. the balls animation is sampled at a very high rate so the collisions are always pixel-perfect, enven on very slow machines. but this requires to multiply the test on the balls. I didn't thought it could have an impact on some machines though, I don't have any loss of fps here.
I hope you won't pay too much attention to these technical problems and have fun with it