Originally released as an Unreal Tournament 2004 mod, a Source-enhanced flavor of the top-down extraterrestrial shoot ’em up Alien Swarm will hit Steam as a free offering next week, Valve has announced.

While the remake was originally intended as a commercial release, Valve hired the team responsible two years ago. In between working on Left 4 Dead and Portal 2, they’ve been busy putting the finishing touches on Alien Swarm.

With a multitude of devastating weaponry at their disposal, players are tasked with eliminating an ominous alien threat as trained IAF marine agents. Up to four-man squads can engage in co-op play. The title will also leverage the entire Steamworks suite, featuring all the perks you’ve come to expect. That translates to matchmaking, Steam Cloud, and real-time Steam Stats. Additionally, 64 achievements are included.

All this for free? Yep, we were pleasantly surprised too. Valve can do no wrong. The alien apocalypse begins July 19.

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