Can you figure out this mind-bending optical illusion?

What is this witchcraft? Photo / YouTube

Ready to have your mind blown?

A finalist in the Best Illusion of the Year Contest 2016 (yes, apparently that's a thing) has racked up more than three-quarters of a million views on YouTube in the past couple of days - and left almost as many confused people in its wake.

The video shows a series of cylindrical tubes being moved around in front of a mirror. As they move, their mirror images show, not cylinders, but square tubes.

What on earth is going on? How is a mirror showing a completely different image to the one we see right in front of us?

See for yourself:

Before you cry 'CGI', rest assured there's no computer trickery involved in the video - that wouldn't make for a proper illusion. Instead, another explainer video shows how the trick is done, as the top of each of the cylinders is shaped in such a way that it gives the illusion of different shapes from different angles. Look, we still don't quite understand it, but the video below has at least got us feeling a little bit less freaked out:

A relatively simple explanation for a seriously mind-bending illusion.