Killing Floor is a first person shooter, allowing each player to move through a 3D environment. Gameplay consists of two game types: Killing Floor and Objective Mode. In Killing Floor Mode, the player fights waves of zombie-like specimens, or ZEDs, with each wave becoming successively more difficult, until it concludes with a battle against a "boss" specimen, called the Patriarch. Objective Mode poses different challenges in addition to fighting against the zombie or zed specimens. Players earn in-game money for each kill, as well as for surviving to the end of a wave. In the time between each waves, players can visit a trader to buy and sell ammo, armor, and additional weapons, such as katanas, pipe bombs, flamethrowers, shotguns, and so forth; the Trader's location on the level varies at the end of each wave, discouraging players from camping in one location. Weapons may also be found randomly across the level. Players are encouraged to work together; they can trade items and drop money, healing is more effective on other players than on oneself, and the team can strategically weld doors shut to provide a temporary barrier from the oncoming horde while funneling the other creatures to specific areas.