Payday: The Heist is a cooperative first-person shooter video game developed by Overkill Software and published by Sony Online Entertainment. It was released on 18 October 2011, for PlayStation 3 in North America and 2 November 2011, in Europe. It was released on 20 October 2011, for Microsoft Windows via Steam. The game runs on the Diesel game engine. It contains seven different missions (including the free No Mercy downloadable content (DLC) released on 25 July 2012), with each mission containing random elements which alter the gameplay in subtle ways with the aim of enhancing replayability. On 7 August 2012, the Wolf Pack DLC was released on PlayStation 3 and PC. This DLC adds two heists, additional weapons, increased level cap, and a player upgrade tree.