A first-person shooter optimized for co-op multiplayer battles, Killing Floor drops gamers in the midst of an English landscape left devastated after a series of military cloning experiments goes awry. There are nine different kinds of monsters to kill, ranging from unarmed flesh-eaters to military-force mutants packing chain-guns and rocket-launchers, and as many as six players can band together, using welders, medical tools, body armor, and over a dozen different weapons to fend off the beasts. Killing Floor includes more than 40 "Steam Achievements" recognizing significant in-game accomplishments, and the "Persistent Perks" system lets players use those achievement to permanently improve their characters. Though designed for multiplayer play, Killing Floor does include a "Solo" mode for offline play, and creative gamers can use the included software development kit to design their own levels and modifications. ~ Christopher Brown, All Game Guide