What a fun idea!
This isn't strictly a criticism, but I do find it odd that there are four options [1010 = UP / 0101 = DOWN / 1100 = SHOOT / 1111 = RESTART] when four bits is 16 combinations. Maybe the other 12 combinations could also perform actions. Not necessarily beneficial actions, mind. Perhaps 0111 could go down twice and 1110 could go up twice. Maybe 1101 is a piercing rifle attack that causes a momentary input delay.
Great work!