Puppy Games’ Ultratron, a Robotron-inspired arcade shooter, is a spectacularly good game. Not only is it fun, but technically it’s great proof that games written in Java don’t have to be slow, buggy, or [insert favorite derogatory Java term here.] And because it’s Java-based, it runs on Windows, Mac OS, Linux, and probably just about any other platform. A bargain at only $9.95. (Update: the price is now $19.95, since the designers decided they wanted to actually make some money. It’s still worth it.)

Recently, Geometry Wars on the Xbox 360 garnered a lot of attention–deservedly–for its old school gameplay and cool graphics. Game-wise, however, Ultratron is probably as good, and its clever power-ups add an element of strategy that is definitely missing from Geometry Wars. And Ultratron’s audio is way, way better.

Now, if only someone would bring back Battle Girl, the pinnacle of retro-gaming tributes. The game, a throwback to color vector games like Tempest, ran on Classic Mac OS and somehow never got ported to Windows or OS X. The source code tragically lingers, silent and undisturbed, on someone’s ancient Mac. A plea: would somebody at the former Ultra-United (the game’s publisher) please release the source code so we can play it again?