
Coming on board to work on popular games such as the Left 4 Dead series, Valve also asked them to begin working on a Source Engine port of their popular mod behind closed doors.

Valve’s Alien Swarm began life as a mod for Unreal Tournament, garnering enough attention from the gaming community that Valve extended job offers to the mod’s creators. The game became an overnight sensation, and it’s no wonder when Valve released Alien Swarm on Steam they did so as a free game with a full set of mod tools available for players to expand on as they see fit. This 4-player top down co-op game features frantic action, an immersive environment full of danger, and enough ranks perks and achievements to keep casual and hardcore players alike interested.

Capturing much of the feel of the Aliens movie franchise, Valve’s Alien Swarm game puts players in the heart of a space colony that has been overrun by alien monsters.
