Killing Floor was released May 19, 2009 by Tripwire. The game was developed by Shatterline Productions. Killing Floor is a first person zombie shooter with RPG elements.

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!

The game originally was a mod for Unreal Tournament 2003 before it was expanded with the Steam SDK for release.

Players select one of seven perks at the start of a match and between rounds. The perk, similar to the idea of a character class, provides bonuses towards certain weapon types, armor, movement, and other factors. Players can level up each perk to increase the benefits it offers.

For example, the “Sharpshooter” perk, which provides accuracy benefits when using scoped rifles, can be raised in level by completing a number of headshots with specific weapons.

The player does not need to play with that perk to raise its level; for example, the Field Medic perk requires the player to heal a number of points to level up, but this can also be done while playing any of the other perks.

Players that die during a wave will drop their current weapon and re-enter the game at the start of the next wave, as long as at least one squad member survives. If the entire squad is wiped out, they will have to restart the game from the first round.

Games have options for difficulty and for duration. With more players, the game adds additional zombies.

A feature called “zed time” awards particularly gory kills, such as headshots, with slow-motion, even in multiplayer mode.

Although, game itself is coated in black humor, which is swirled inside small popular culture and steam punk references. Not everyone’s cup of tea at that, but I assure you everyone can take the joy of killing mindless clone armies even it’s given in a literature covered in vain and desperation.

In a sense, Killing Floor and Left 4 Dead 2 really made zombie shooters a viable new category of games.