1.No formula,more challenging. 
2.Enhance the concentration,logic and patience. 
3.Firm material and rigid structure. 
4.Replace video games and reduce the chance of nearsightedness. 
5.A great toy for bridging generation. 
6.Age 5 children and adult.Good for preschool children,mentally degraded elder and disabled students. 
7.Spherical shape.Easy to hold and play with.