Gravit Designer: Learn to Draw a Schroeder Stairs | Optical Illusion
Schroeder stairs (Schröder's stairs) is an optical illusion which is a two-dimensional drawing which may be perceived either as a drawing of a staircase leading from left to right downwards or the same staircase only turned upside down, a classical example of perspective reversal in psychology of perception. It is named after the German natural scientist Heinrich G. F. Schröder, who published it in 1858. ( https://en.wikipedia.org/wiki/Schroed... )