Killer Bees and UFO are both great games. It's a little discouraging that UFO reuses the shield and shots for explosions, meaning that following an overly-successful chain reaction one may be a sitting duck for awhile, but otherwise it's a great game. And it's been ages since I've had my hands on Killer Bees, but that was a truly amazing game. Too bad neither UFO nor Killer Bees seem like plausible games for a 2600 except maybe using the Supercharger hires flicker hack.