Our son has a crush on this game at a demo on a Christmas market. This is a particularly addictive game which has the merit of diverting children from their video games! promise! Principle: oscillating in the perspex ball in all directions, you move a small metal ball on a circuit 3d, the steps are numbered from 1 to 100. No possibility of backup if we abandon ongoing. The route is dotted with various obstacles but progresses quickly if we are persistent. Our 11 year old son is quickly reaching the end of the course. The whole family gets started and everyone a chance, from 7/8 years. Perplexus also learns patience ... and manages to find shortcuts and arrive more quickly at the end. We bought the "epic" model listed expert. Much harder and 125 levels! But just as addictive.