Yet this cat breeding game comes with serious pedigree. McMillen was one of the early pioneers of the indie game scene, as illustrated in the definitive 2012 documentary Indie Game: The Movie. He made Super Meat Boy, a tough platformer as gory as it was popular, and The Binding of Isaac, a deeply eccentric roguelike action game which sold an estimated 10mn copies — a figure that dwarfs even many blockbusters.