This is a Mausritter-inspired hack of Tiniest Dungeons & Dragons, a minimal business card D&D tribute which is itself a derivative of the excellent Lasers & Feelings.

Mausritter is already a fantastic and minimal game, and I highly recommend playing that instead of this. It's a million times better. This game only exists so I can play mouse-sized adventures with my young kids when we are out and about and I am only carrying a handful of dice and this index card on me. If you find yourself in a similar boat, give it a whirl and let me know how it goes.