The Spinning Silhouette Optical Illusion
This is a very bizarre dancer optical illusion. At first glance the spinning lady appears to be circling in a clockwise motion. But if you look at the spinning dancer long enough - the lady will appear to change direction and start spinning counter-clockwise.
For me the switch didn't just happen - I had to look at her shadow and picture it going counter-clockwise. After about a minute, my brain flipped and the lady just started spinning backwards. Actually - I can't seem to convince my brain to get her to start going clockwise again. But it is pretty wild when you see the switch happen.
This spinning illusion has also been referred to as a Right Brain vs. The Left Brain challenge.
It's a tough one and it takes a lot of focus.