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.