Amazing animated visual illusion – rotating female figure

I have seen plenty of visual illusions - both static and moving - but I have never seen a rotating human figure as an optical illusion. Took a while to even convince myself it was not a joke.

I did work it out in the end (after a hint). The secret - at least for me - was to concentrate in the bottom-right corner on the feet shadows and force my eyes to track the outer foot’s shadow the way I wanted it to go.