Respawn started pre-production on its then-untitled game back in 2011, originally for current generation consoles. As the team tried to pinpoint what their first project would be, they searched for a technological foundation to build on. They found it in an unlikely place: Valve’s Source engine. While few titles outside of Valve’s own games and independent mods have used Source this generation, a number of factors made it a good fit for Respawn. "We were kind of interested in Source early on because it’s very familiar to our designers," said Richard Baker, a software engineer at Respawn who previously worked on Call of Duty 2, Modern Warfare and Modern Warfare 2. Source also suited Respawn’s desire to hit a constant 60 frames per second on both the Xbox 360 and the PS3, where other third-party engines weren’t up to the task. "The ironic thing is that we wanted an engine that would work on PS3, because that’s the riskiest platform in current gen. When Portal 2 came out and it seemed to be a pretty decent PS3 game, that was the point when we decided to go with Source. And then we stopped supporting PS3."