Payday: The Heist is a 2011 downloadable cooperative first-person shooter video game developed by Overkill Software and published by Sony Online Entertainment. It was released on October 18, 2011, for PlayStation 3 in North America and November 2, 2011, in Europe. It was also released on October 20, 2011, for Windows via Steam software in both the United States and the United Kingdom. The game runs on a modified 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 August 7, 2012, the Wolf Pack DLC was released on PS3 and PC. This DLC added two new heists, additional weapons, and a new player upgrade tree. On February 1, 2013, Overkill Software announced a sequel to Payday: The Heist titled Payday 2. It was released on August 13, 2013, via Steam for PC, and from August 13–16 for Xbox 360 and PlayStation 3.