We made it in the very newbie-friendly Game Maker: Studio. I've only been earnestly teaching myself to code for the last six months or so, so the gargantuan amount of tutorials and learner's resources available for it are a bit part of what made this possible.  Musik Kombat did most of the sounds and music in FL Studio, and the art (outside of a few menu button placeholders that I never got around to replacing!) was done in an open-source art program called Krita.