Autumn motion

There is an unexpected effected if you move quickly while observing the center !!!
You can for example move quickly from top to bottom the scrolling bar (on the right) while looking at the central rectangle, you will see, it is surprising.

This illusion, created for Ophtasurf, was inspired by the illusion of Akiyoshi Kitaoka.

The central rectangle seems to float. The brain has difficulties to express this image according to what it knows, it does not manage to determine contours