Dynamic infestation was a proposed feature of Natural Selection 2 as far back as 2006 (warning: video with significantly louder audio), when the game was still running on the Half-Life 2 Source engine. It’s only now, with build 163, that it’s has been added to the game’s custom engine, along with a host of other features and bug fixes. The infestation works very similarly to the creep in Starcraft – alien structures can only be built on top of it.
Natural Selection 2 is a multiplayer FPS/strategy game where players can take on the role of either a commander, who has a top-down view of the level, or a variety of grunts that are controlled from the first-person view. If you pre-order the game you can start playing the beta immediately.