Optical Illusion: After 20 seconds, your surroundings suddenly change

Look at the center of the screen for 20 seconds. Once the time is up, look around. You will find that the space around you seems to be contracting.
The effect wears off after a few moments.
Neurologically, it has not yet been clearly clarified how the illusion comes about.
A possible explanation: The brain tries to compensate for the movement of the animation. If you then look at a stationary object, it takes a few seconds for the brain to adjust to the new circumstances.