Just as Snow White taught you, you should never trust a mirror.
This piece of sorcery features a mirror that seemingly turns squares into circles, then vice versa. But interestingly, it's not strictly the mirror that is fooling you – it's a combination of the shapes used and your fickle perspective.
Speaking about this illusion, the competition said: “The direct views of the objects and their mirror images generate quite different interpretations of the 3D shapes. They look like vertical cylinders, but their sections appear to be different; in one view they appear to be rectangles, while in the other view they appear to be circles. We cannot correct our interpretations although we logically know that they come from the same objects.”
Watch it below. If it’s still boggling your mind, you can check out this explanation by Martin Missfeldt, although you might need to whack on your Google Translate if you’re not fluent in German.