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What: This silhouette illusion is likely one of the more difficult ones to reproduce. Having said that, the effect and the sense of wonder when it works are probably also among the most astonishing to me. Here, you can see a spinning duck. The thing is, with a silhouetted image, there isn't really sufficient visual information to determine whether it's spinning clockwise or counter - clockwise because there are multiple positions where the image appears exactly the same. The most well - known version of this is the spinning dancer by Nobuyuki Kayahara. In my version, I've used a simple duck. I experimented with several different models, but interestingly, the code for rendering this in 3D was using a rubber duck, and it seemed perfectly fitting to use it. Moreover, in many ways, the simplicity of the duck made it much easier for me to change the direction with my mind.

How To: You can use the configurations to alter the duck's direction, but you shouldn't have to. That being said, if you can't make it rotate using your brain, you can click the button. The change in direction will make your brain perceive it as spinning the other way. Then you can watch it for five to ten seconds, briefly close your eyes and switch it back. When you open your eyes, you shouldn't notice the change. I've been able to reverse its direction semi - regularly by blinking widely when the duck is facing me (or facing away). Another fun thing to do is to place a mirror next to this (or your phone next to a mirror). You'd expect to see two ducks rotating in different directions, but that's not always the case!