In the first step two elements from CW end shift half-a-side ACW. The second from ACW end shifts one side CW. While ACW end shifts to CW end and is replaced by a new element. In the next step the CW-end element shifts one side ACW; the second and the third from CW end shift half a side CW; while the ACW end shifts to CW end and is replaced by a new element.
In each step the whole figure rotates by 90° CW. One of the elements remains constant while others shift one step CW. One element is replaced by a new one. Replacement occurs on either side of one end of the line.