This just came out on Steam. Its a free mod for the source engine, released with dev tools and source code. I figured I'd give 15-30 minutes to it last night with some friends that were raving about it and ended up giving in 3 hours. Its very fun coop play, and I'm looking forward to looking at the dev kit that came with it after I beat the final level. I'm posting this because I believe we all need to relax now and then and play a game, but for those of us that love programming, its great when you can modify the games which we play. I think thats what keeps the PC gaming community strong is the need to modify our games in ways that consoles lack. Good Luck!