Escher bird
How to make a Escher-like drawing based on a square and rotational symmetrie?
Draw a square
Change the top line and rotate it over 90° anti-clockwise with respect to the top corner on the right
Change the bottom line and rotate it over 90° anti-clockwise with respect to the bottom corner on the left
Then rotate the "bird" over 90° anti-clockwise with respect to thebottom corner on the left