see below a picture of the corresponding
it's made of paper and I had trouble
keeping it together to take pictures but
it gives a fairly good idea of what the
result would be. On the next picture I have
outlined in RED the lines that would be involved
in the rotation of the front purple face:
Don't you agree that they all lie in a
single plane since their distance to the
plane of the purple face appear to be equal ???
I am NOT 100% sure, please let me know what you think.