Ten Halloweens ago, the absurdly popular Natural Selection mod transformed Half-Life into a multiplayer shooter with real-time strategy. Today, its long-developed sequel is finally up for pre-order on Steam, attached with a very convenient 'October 2012' release window. Yup, we'll eat our pumpkin hat if Natural Selection 2 isn't out by October 31. Until then, the game remains in beta with over 40,000 active players according to developer Unknown Worlds.

Natural Selection 2 now offers a tactical team-based shooter in a proprietary engine, with one side the marines, the other the aliens. One member of each team plays the "Commander" role, overseeing the fight from above and influencing it through RTS features like defenses, buildings, and upgrades.

Pre-orders on Steam are being rewarded with Natural Selection 2's deluxe version. That includes the official soundtrack, a digital art book, and some in-game armor amongst other goodies, all for $24.95. Sadly, there's been an oversight regarding a pumpkin hat.

Update: Clarified release window and corrected engine information.