A foil carrying 4 LEDs, rolled up into a cylinder. The LEDs flash one after the other and the sequence gives an illusion of movement, of rotation. If you take a close look, you can identify each LED lighting up. The frequency could be a bit faster. Without concentrating on the LEDs the illusion works. Why 5 stars? Because game of bricks managed to minimize the size of the construct, that it fits into a 1x1x1 cylindric brick - as shown on the photo, or into the center cylinder of a 2x2x1 brick, and so on. They make realy good rotating lights.