Most Blu-rays and DVDs these days come with filmmaker commentary tracks, but it isn't too often you get to hear a game developer give play-by-play while running through something they created. That's the thrust behind the latest episodes of Double Fine Productions' "Devs Play" YouTube series, spotted by Polygon. Here we have one of Doom's co-creators John Romero playing a handful of maps from the legendary first-person shooter that runs on basically any platform. He breaks down everything from the work that went into differentiating it from id's other FPS Wolfenstein 3D, how the team used texture irregularities to denote secret rooms and even how he's watched speed runs that not even he can replicate. Oh, and he designed the first level last, incorporating everything he'd learned throughout the other missions to make the initial one the most interesting.