[PyWoody]

Try closing one eye and tilting your head 90°

[kerpotgh]

I can see it irrespective of how many eyes are open or any tilt angle.

[javawizard]

So you can see it with zero eyes open? ;)

I also see it with any number (>= 1) of eyes open and at any angle. Wonder if GP's phone was on night shift or something similar - the article mentions that color changes impact the illusion's visibility.

[d4mi3n]

No night shift, for what it’s worth. Another commenter mentioned astigmatism, which I do have. I was not wearing my glasses at the time.

Curious to see if anybody with expertise on the topic of optics or visual perception chimes in with some insight.

[kerpotgh]

Interesting, I have astigmatism so I tried it without my glasses and with both one and two eyes open at different angles and I still see the illusion (with no change in intensity of the “bobbing”)

[yazzku]

Can you see it with three eyes opened?

[labster]

I can’t but I’ll ask my yoga guru tomorrow.