Valve it seems has not been working head down just on Portal 2. They just released Alien Swarm, and it’s completely free through their online distribution portal, Steam.

Those of you who remember the board game Space Hulk will be familiar with the theme. Alien Swarm is a top-down 3D squad-based tactical shooter. The freebie has both single- and multiplayer action, where up to four players can hook up to hunt down and slaughter alien bugs. The title offers more than 40 unlockable weapons and gear items, to help players in their space bug hunting. Valve is also offering the game’s complete code and mod tools to the development community. As with the game, the code will be available free of charge!