I solved this by using the red marbles to modify register A, and the blue marbles to modify register B. I posted this specific route as a new puzzle, so if you would like to try and solve this on your own first, here’s a link to the post and the initial board state to get you started: Puzzle 52 with a Twist
For those here who just want to see how I did this, here is my solution:
https://www.lodev.org/jstumble/?board=lr0eel0relerrllee0x0eerxlbee0b0gberbgbgbee0bbierlxreer_16_16
I used every gear in the standard kit to get it to work, and the reason it’s cursed is because of how complex it is, yet each pass of a red marble and 2 blue marbles creates a perfect loop for the gears. I think this is the first time I used all 8 gears together in a group like this, and the marble falls super slowly every time. The marble often gets stuck in the gears and requires manual intervention to give it the momentum it needs.
I guess seeing all the red marbles in the top made me believe that I had to use them, even though the simplest solutions only use the blue marbles. After enough bashing my head into the wall trying to get it to work, I experienced possibly the funniest moment with this thing when I built a working solution that seemed to run in slow motion as soon as the marbles reached the gears. This is not the optimal solution in terms of the parts used, or the simplicity of it, but it is the optimal solution for generating laughter