Killing Floor is a Co-op Survival Horror FPS set in the devastated cities and countryside of England after a series of cloning experiments for the military goes horribly wrong. You and your friends are members of the military dropped into these locations with a simple mission: Survive long enough to cleanse the area of the failed experiments!

• Cooperative gameplay for up to six players against multiple waves of specimens
• Persistent Perks system, allowing players to convert their in-game achievements into permanent improvements to their character's skills and abilities
• Slow-motion “ZEDtime” to better watch those crucial and violent creature deaths, even in multiplayer
• Solo game mode for offline play
• Nine different monster types trying to eat your face off, armed with everything from teeth and claws, to chainsaws, chain-guns and rocket-launchers
• 12+ weapons for the players to chose from, ranging from knives and fire-axes to pump shotguns, rifles and a flamethrower
• Equip your team with welders, medical tools and body armor to help your odds of survival
• Choose which Perks to play with to best balance out your co-op team against the horrors
• Open, non-linear play areas: choose when and where to fight — or run; weld doors closed to direct the monster horde down alternate corridors
• Fully-configurable, allowing players to change the difficulty level, number of creature waves, or even set up their own favorite waves of monsters
• Includes Windows-only SDK for the creation of new levels and mods

To activate the game, you need a Steam Account

• Login or register at the official
  Steam Website and download Steam client
• Install and start application, login with your Account name and Password
• Click the Games Menu.
• Choose Activate a Product on Steam...
• Follow the onscreen instructions to complete the process
• After the successful code verification, go to the "MY GAMES" tab and start downloading.