Nuclear Asteroids (beta testers wanted)

For those of you who didn't see my last blog post, I'm working on games that teach chemistry concepts. This one is about nuclear reactions and decay. (If it's been a while since you've last taken chemistry (or physics), I'd recommend skimming this before playing.) The game is now at a beta state, so I'm putting it up here as an open beta for anyone to download. If you encounter any problems, post them here. I do ask that people not redistribute or mirror copies of the installer. You can download from here, and the scoreboard is here.

So, try it out, tell me if it's too easy or hard, or there are any other bugs or gameplay issues I should know about.