Alien Swarm re-released with Source upgrade [VIDEO]

Alien hunters, rejoice. The third-person shooter Alien Swarm hits the Steam platform later today – and developer Valve is releasing the game with the complete code base, meaning amateur designers will be free to tinker around with Alien Swarm until the cows come home. Alien Swarm, of course, is itself a modification of Unreal Tournament 2004, a top-selling video game built on the Unreal Engine.

The newest Alien Swarm, which hits Steam later today, has been updated for the Source Engine. Better yet, it's completely and totally free. Alien Swarm newbie? Here's the low-down: There are a bunch of alien bugs with giant claws shrieking their way through some sort of far-flung outer space outpost, and you have to stop them, using guns and other interesting virtual toys.

The game features four-player co-op – so you can shoot alien bugs with your friends – and according to Ars Technica, a load-out of "over 40 weapons, eight characters across four classes, and persistent items to unlock." Fair enough. The trailer for Alien Swarm – see below – shows off armored avatars and a giant-clawed monster bug (which looks a lot like one of the Corpsers from Gears of War).

Here's the blurb from Valve:

In addition to the game, Valve will also release the complete code base for Alien Swarm. This includes updates to the Source engine SDK and full Steamworks integration. If you've ever thought about developing a mod on the Source engine with Steamworks, this release provides more insight and examples for using Steamworks in game production.

In related news, last month Valve announced that Portal 2 would not be done in time to make its scheduled "holiday season 2010" release date. The much-awaited game is now expected to hit Windows, Mac OS X, the Xbox 360 and the PlayStation 3 by 2011.