"Dark Deco" is an animation style created by Bruce Timm and Eric Radomski used in Batman : The Animated Series. They knew that Batman was a dark character so the two of them knew the show had to be dark as well. Backgrounds would be painted on black paper and anything that was black in the show was left unpainted. Kids WB once told Bruce Timm that his show was so dark he was about to reach the legal limit of how dark his show could be.