IT'S hard to appreciate optical illusions in an age of CGI trickery, but this one's up there with the best of them.
One trick has managed to gain three-quarters of a million views in only a few days on Youtube, and has won the Best Illusion of the Year Contest for 2016, reports news.com.au.
The illusion involves a series of seemingly square-section tubes turning into cylinders when reflected in a mirror.
Can you tell how they pulled it off from the video below?
If you're like me and hate not knowing, here's the explanation thanks to the Make Anything 3D printing channel.