I'm back today with some bug fixes--thanks to Trip for helping me find the problem with the aliens not respawning after a restart. I also made a few other tweaks and added some new features, namely a brief (perhaps too brief?) period of invincibility after your ship respawns, and three new types of power-ups: extra life, speed boost, bonus points, and of course ever-popular cannon upgrade. I also took another person's advice and added a "color reminder" swatch just below the score. I'm still getting occasional missed matches. I went back through my code today and still don't know why that is happening. It seems to come in spurts; you can play several rounds without a hitch, but then get it two or three times in a row.