[Digo]

I know now it´s done, but I would like to share my point of view. It´s not useful now, but may be for next year.

The tetra should be made to spin for sure or not to spin for sure. This doubt prevents you from thinking in many possibilities. You will not design a claw/arm counting that the tetra does/doesn´t spin knowing that this situation may change later, or that the tetras may be different from each other. So you need to give up thinking both ways and think about something that works both ways. I guess that limitation could have been avoided.

And I don´t think "that´s part of the challenge", because this way you don´t know what the challenge is.