Ladder on the Wall Illusion

Topic:
Geometry
This applet was inspired by the YouTube channel Sonhos com Dimensão, in particular this video https://www.youtube.com/watch?v=FwA-eLtjFl4. In the applet you can move the blue points so the ladder moves up or down the wall and so the width of the ladder increases or decreases. It is also possible to move the two rungs of the ladder. The slider changes the elevation of the sun and the resulting shadow cast by the ladder. After playing with these features, use your mouse to rotate the view, and you will see the illusion. The "recycling" symbol resets the view.