for videos please see my partner Jerry’s doc: link
we were asked to guess how this toy worked and then took it apart.
we saw that both his head and arms would rotate if we pressed the yellow button, so we were guessing that there was something inside that made them rotate separately, and there was a spring that could control the position of the button.
when we took it apart, the parts in it suddenly jumped out. then we found that two rotations were not independent. the neck was a helix and there was a little ball on part black that could fit into the neck and made it rotate, and when we pressed down and released the button, part black would move with the spring. part green was connected to part black (by the notch on part black and little ball on part green) so it would also move, and part yellow i.e. the arms was the connected to part green. Part blue was used to make part black to move only vertically.
it took us long to restore the toy. since we didn’t see the correct position of everything we misplaced part black for 180 degrees at first, and then we found it hard to hold every other part when we tried to place the red part. finally we did not first place the button inside and then covered with part red but instead held part red and the button together and then we succeeded.