http://store.steampowered.com/app/630/ * Tactical, 4 player co-op action game with a top-down perspective
* Complete game code and mod tools
* Unlock persistent items by gaining levels
* Over 40 weapons and equipment with countless loadout configurations
* 4 unique classes and 8 unique characters
* Matchmaking, Steam Cloud, Steam Stats
* 64 achievements
* Tile-based map generation tool
* Powered by Source and Steam