De vandrene brikker

De vandrende brikker: Your hands are empty except for 4 small pieces that you place in a "square" on the table - approx. 30 cm between them. One piece is covered with your left hand and another with your right. When moving your hands away again, the piece below the left hand has disappeared, and below your right hand there are now two! The trick is repeated until all four pieces have appeared below your right hand.
The color of the pieces may vary from photo.