Play Natural Selection 2 for FREE starting now through Sunday at 1PM Pacific Time. You can also pickup Natural Selection 2 at 50% off the regular price! Natural Selection 2 is an immersive, multiplayer shooter that pits aliens against humans in a strategic and action-packed struggle for survival. It seamlessly combines a shooter/FPS gameplay with a strategy (RTS) game. If you already have Steam installed, click here to install or play Natural Selection 2. If you don't have Steam, you can download it here.