The basic shape of the ENI is cylindrical. The cylinder is divided by several ÃÌ´Ì¥ring-shape sections.ÃÌ´ÌÕ These sections can rotate independently. Each ring section includes multi- individual parts, with one piece missing. These parts can travel along each ring by using the missing piece (empty space). By rotating and sliding the pieces in and out of the empty space, a multitude of solutions is possible.