If you can see it turning both ways, your IQ is
(supposedly) above 160 -- which is almost a genius.

I found it to be like those pictures that if you looked at them just right,
they became three D. When I would glance around, she would change
directions, and at times, she makes half a turn in one direction, then
reverses, then rerverses, etc, until I move my eyes, and then that would
change. It is definitely an interesting demonstration.

Steve