Killing Floor

Killing Floor is a cooperative first-person shooter video game developed and published by Tripwire Interactive. It was first released on May 14, 2009, for Microsoft Windows, and subsequently ported to the Apple Mac OS X platform, with a release on May 5, 2010.

Gameplay
Typical gameplay consists of a single game type, single- or multi-player, in which the player fights waves of zombie-like specimens, with each wave becoming successively more difficult, moving through each area of the level, until it concludes with a battle with a "boss" specimen, called the Patriarch.

Alex Quick, the level designer and texture artist, stated that "there are a whole bunch of ideas on the drawing board that we can add in after launch, including the 'Story' mode from the mod, for instance."

A wave is completed when all the specimens are dead. Players can choose where to run and fight. Up to six players can team up in an online cooperative battle with the specimens. The game sessions are fully-configurable, so players can change the difficulty, number of enemy waves, or specify which creatures compose the waves, although certain combinations do not allow perk advancement. As the players progress through waves, the tougher-grade specimens are more commonly encountered. A software development kit (SDK) and level editor are included to aid in the creation of modifications and levels.

There are a wide array of weapons, including melee weapons, shotguns, rifles, sidearms and other weapons. Players may accumulate money through killing specimens, surviving waves, from other players, and selling acquired weapons. This money can then be used for weapons, supplies, and ammunition at "the Trader" on completion of a wave. Where there is more than one trader point on a map, the trader location is randomised, as a mechanism to encourage players to explore the map. Current trader location is indicated to players at all times by way of a red arrow.

A feature called "zed time" allows the player to see particularly gory kills, such as headshots, in slow-motion, even in multiplayer mode. It can also give the players an advantage for a brief time to carefully aim their shots.

Tactical gameplay elements exist, such as the ability to weld doors shut to direct the flow of the enemy hordes, and the gameplay encourages teamwork by giving less of an energy penalty when players heal each other, instead of themselves.

There is voice chat, and automatic, randomized voice responses from character interaction and selectable voice commands, for communicating with other players. Randomized music plays during set up and combat stages in each level. In set up, the music is generally ambient and quiet. In combat, it is louder, faster-paced heavy metal.

There is a "Perks" system, which gives the player certain strengths and/or abilities. Players have seven to choose from. These are leveled up as their requirements are met, improving their effectiveness. For example, the Commando perk gives the player a discount on automatic weapons, improved effectiveness with automatic weapons, faster reloading with all weapons, and grants detection of cloaked specimens within a certain radius. However, use of the perk is not required for advancement, i.e. the Commando perk requires damage dealt with automatic weapons as a component of advancement, however, using an automatic weapon whilst being a Medic or Sharpshooter will still advance the Commando perk.

Perks
The perk system, as explained above, uses 7 different perks: Commando, Berserker, Firebug, Sharpshooter, Support Specialist, Demolitions, and Medic. Commando specializes in automatic weapons, and detection of enemies. The support specialist specializes in shotguns, and gets bonuses in welding doors shut, grenades, and carrying more weapons. The medic specializes in healing teammates,and gets bonuses in the use of the MP-7 medic gun, resistance to bloat bile, and speed. The berserker specializes in melee weapons, and gets bonuses in speed, resistance to clots, and damage reduction. The Demolitions specializes in high explosives, and gets bonuses in such things as resistance to explosions. The firebug specializes with the flamethrower, and gets fire resistance and the use of fire-grenades. The sharpshooter specializes in rifles and sniper-type weapons, and gets headshot bonuses.

Story
The game takes place in London, England. Horzine Biotech, a biotechnology company, is contracted to conduct experiments of a military nature involving mass cloning and genetic manipulation. Something goes horribly wrong during the process of the experimentations, and human subjects begin to exhibit grotesque mutations and disfigurement. They become increasingly hostile, and eventually overrun the internal security forces of the corporation.

Hours later, the first waves of the specimens break out onto the surface, disrupting a peace protest outside the well-known military contractor. Despite the best efforts of local police, the civilians are quickly overwhelmed and consumed by the seemingly endless supply of clones now streaming from the gaping maw of Horzine Biotech's headquarter. Having escaped their sterile prison, the creatures began to fan out to neighboring areas, devouring the helpless citizens of London while the Metropolitan Police bravely but fruitlessly attempt to stem the tide of mutated flesh now spreading across their city.

Desperate to contain the outbreak, the British government begins to organize ragtag teams of surviving British Army soldiers and Special Branch police officers to fight back against the hordes of mutated "specimens" now running amok throughout the capital and its outskirts. The player takes the role of an anonymous member of one of these teams as they partake in a variety of missions in and around the city of London.

Development
Killing Floor was originally a total conversion mod for the game Unreal Tournament 2004, first released in 2005. The lead developer Alex Quick was first approached by Tripwire Interactive about porting Killing Floor to their game Red Orchestra: Ostfront 41-45, but Quick did not follow through. A few years later, when their user base started to dwindle, Quick contacted Tripwire again to negotiate the port to Red Orchestra, and its distribution via Steam—similar to what Tripwire had already done with another Red Orchestra mod Mare Nostrum—and then later, the retail game. The mod version had its fifth and final official update in July 2008.

The full retail version was announced in March 2009. With the assistance of the original mod team, Tripwire would be the new developer.

Killing Floor was released on 14 May 2009.

Downloadable content
Tripwire Interactive has to date released two major content packs free of charge, "Heavy Metal" and "Level Up", which add new weaponry, levels, and other content. Also available are two character packs, Outbreak and Nightfall, which add four new player avatars each.

Reception
Killing Floor was the top-selling game on Steam shortly after it was released (as of May 19, 2009).

Killing Floor has won a number of awards including Overall Best PC Game of 2009 in Voodoo Extreme's Reader Choice Awards. It also won 2 other categories in Voodoo Extreme's Reader's Choice Awards: Best PC Shooter of 2009 and Best PC Game Expansion or DLC of 2009.

EuroGamer commented that "though not perfect", it was "clever and relatively cheap". GameSpot commented that the game graphics compared poorly with contemporary shooters, and that the voice acting was bad, but considered that the sound effects were very good, and that despite its flaws, "you can't help but enjoy it." Some reviewers also considered that the lack of any real plot or aim for the players other than killing specimens, the small number of existing maps, and the repetitiveness of the gameplay reduced its replay value. Killing Floor has a Metacritic score of 72%.