Neat! I had an old "Omni" magazine back in the early 80's (yes, I'm old) that had a page with a black and white pattern on it like this one only it was round. One would put it on a turntable and then you would stare at the center for a while. The after image had the boiling effect like this one. The magazine also had a picture of a cloud pattern that one could look at after looking at the wheel and the clouds would "boil"!