We used parts of a Left 4 Dead level as the first bit of level geometry to start building in Source 2, so a bit of that got out. IGN also got the scoop on what was really behind those Left 4 Dead 3 leaks and rumors that went on until Valve had to shut them all down only a couple of months ago. we didn’t want to make that same Half-Life 2 mistake again of working on Source 2 and the next Half-Life game at the same time, because that created a lot of pain the first time we tried to do that. I think at that point we realized, ‘Okay, maybe this episodes thing, it was a good concept, but we're not executing terribly well as far as getting things out quickly enough'.

We found ourselves creeping ever forward towards, 'Well, let's just keep putting more and more, and more, and more stuff in this game because we want to make it as good as we can', and then we realized these episodes are turning more into sequels. We think players are going to prefer that from waiting six years and going through however many delays we went through'. Let's just bite off little chunks and then release more often.

We understand the characters, we understand the story, we have most of the mechanics. That's why we started doing the episodes where we thought, 'well, we have the stable technology now. After working on Half-Life 2 for six years we decided we didn't want to go dark for so long.

Left 4 dead 2 source 2