An epic bug hunt featuring a unique blend of co-op play and squad-level tactics. With your friends, form a squad of four distinct IAF Marine classes. Plan your attack using an unlockable arsenal of weapons with countless loadout configurations against a wide variety of aliens. Blaze your way through an overrun, off-world colony, eradicating the alien infestation in environments ranging from the icy planet's surface, to a subterranean lava-flooded mining facility.
Can't argue with a free game, especially with the quality this provides. There are a multitude of potential this game had, and provided hours of amusement for a group of friends.
Control-wise, this game does the top-down view very well, with responsive controls that will keep up with the intensity of the action on screen, as well as full customizability from the console commands provided by the Source Engine.
Graphics, well, they are pleasing, while showcasing the lighting effects and fluidity of the action. It won't set the world alight, but still quite good to today's standards for a free game.
Gameplay, the hit detection does an admirable job on doing its job, but there will be some weapons that will be crowd favorites over others for making things easier. However, the pacing can spike on a few occassions if the team isn't careful, or the Onslaught Mode is turned on. Moreover, there's only one official campaign included with the game, while replayable, it will wear over time. The community has done a great job in adding more to the game in terms of campaigns, but Valve rarely supports this game, which leaves much to be desired in fixes for some glitches and overall longevity. Nevertheless, it's free, it's totally recommended if you can get 3 other friends to play along for a few hours. But beyond the achievement chases and personal challenges, the game needs more to stay on your hard-drive for a long time.