Over on itch.io, there’s a game jam going con called the Pleasure-not-Business Card RPG Jam. Entrants create a RPG or RPG supplement that fits on a business card.
I’ve created my own entry: Planck. Planck is a complete sci-fi RPG compatible with Traveller, Cepheus Engine, and other 2d6 Sci-Fi RPGs. It’s free to download.
I was gonna call it Cepheus Planck, to be a smaller version of Cepheus Quantum, but I couldn’t figure out how to put the OGL on a business card.