Whats it do? Actually not too much, I think only two games ever used this, Gyromite and Stack-up. The R.O.B. robotic operating buddy would watch the screen while you were playing nintendo and push the A or B buttons on the player 2 controller to lift up the "walls" that were in your characters way. You had to put the 2nd controller in its holder and it would spin a gyro and place it on the red or blue buttons to basically press the a or b buttons for you. Old video games bring back good memories!