Stationary disc

HOW

1. Grab the discs on either side of the mirror.
2. Tilt your head to the left side and stare into the mirror.
3. Without changing position, move the disc on the right side.

WHY

Moving the disc leaves you puzzled and perplexed because your brain was expecting a movement that did not happen. The mirror image of the left hand replaced the right hand in the brain.