Steam's holding another free weekend promotion, and this time it's multiplayer shooter Natural Selection 2. You can play the action game for free until Sunday, October 30th. If you want to play past then, you can pick it up for a discounted price of $5.

Those who bought the vanilla game before the release of the Deluxe Edition--which includes an artbook, soundtrack, and in-game skin--can upgrade for $5. And if you're new and want to jump in with three other friends, the Natural Selection 2 four-pack currently costs $12.50, down from its regular price of $25. All of these sales last until Tuesday, November 1st, at 10 AM PT and can be seen here.

Natural Selection 2 blends shooting with real-time strategy elements. It's a humans vs. aliens, first-person shooting affair, with a commander watching over each team in an isometric perspective. The commander is responsible for the RTS parts of the game, such as building structures, collecting resources, and researching technologies. For example, the commander can drop health packs and sentries to assist their team.

Additionally, Natural Selection 2 is holding a Halloween event this year with a mode called Infested, where you race to repair areas of an outpost.

Source: GameSpot