Six Fold

Snake folded onto a paper cube. One ink line runs across six panels, eating marks that make it longer and faster, and crossing an edge rolls the cube so the face you just left becomes a wall. There is no floor and no finish line; the only thing that can stop the run is the line biting itself, which gets steadily easier to do as the trail fills faces you will have to cross again. Three starting speeds, and the fastest one is called Feral for a reason.