But well... I’m not sure how great a test this is for creativity or logic. It just looks like a cool optical illusion to me. Essentially the image is 2D with the moving foot going left and right, but our minds assign a 3D bias to it... which...

Oh, I noticed a trick. If you focus on the calf muscle that’s standing, and follow the moving foot when it crosses calf, you could make it switch directions. For example, if you’re looking at the calf muscle and then follow the moving...

At first look it’s always clockwise, and then after a bit I see it counter clockwise. After a bit of looking I could see it either way by command.