Following approximately a kajillion years of waiting, RTS/FPS hybrid Natural Selection 2 has finally launched, and naturally, there's a trailer to promote said launch. Three minutes in length, it does well to illustrate the two major gameplay elements: building and shooting. As you'll see, both the monster alien dudes and the humans build up their bases then get all violent on each other.
For those on the fence, know that NS2 is a true PC game in more ways than one: it includes mod tools and source code, Steam Workshop is supported, and free maps, weapons, and abilities will be added over time. It's available now on Steam for $25.