I've been playing a little Alien Swarm this week. It's a pretty good game as is, but that's not why it was provided free of charge. No, it was provided free of charge so you kids could mess with it.
And we're already seeing the fruits of these labours. Shrimpsess over on the Steam forums has posted a long list if command line tweaks you can make to the game, which with just a few characters can introduce a range of features other developers would be charging for as premium downloadable content.
Like the introduction of a "director mode", like the one found in Left 4 Dead, that intelligently spawns enemies. Or an actual, working first-person mode for the game. There are also some minor (though welcome) changes, like shifting the Gears-of-War-a-like "fast reload" system underneath your guy instead of hiding it in the corner and enabling 360 controller support.
Valve hired on the team responsible for Alien Swarm two years ago. Since then, they've been busy working on the Left 4 Dead series and now Portal 2, but they've managed to squeeze out a little extra time to update Alien Swarm as a full Source release.
Alien Swarm is a top=-down four-player shooter, similar to arcade games of old. Players one of eight unique characters with four different classes, and battle their way through hordes of aliens using more than 40 different types of weapons and equi9pment. Players will gain levels as they play, unlocking persistent items along the way.
Not only is Valve releasing the game for free on Monday, it's releasing the game's entire code base and modding tools as well. With a simple, tile-based map editor, modders should have a field day with Alien Swarm.
Look for it on Steam come Monday!