On Monday, Valve released a new free (!) Game Alien Swarm

Alien Swarm on the first trailers is a hell of a mixture of Left 4 Dead and Alien Shooter. 4 players, as in L4D, and top view, as in AS. The best part is that the game will be distributed on Steam absolutely free.
The rest of the standard set: 64 Achievement, 40 types of tools for the formation of communism in the camp of the cockroach, 4 classes and 8 characters.
After watching the trailers and gameplay, it seems that this is a future hit.
Trailers: two pieces .
Game page on Steam.
The site of the game.