● This design is rich in color blocks and adopts solid color that children prefer, which is in line with the color perception sensitivity of this age group. ● In terms of ergonomics, children's hands are small and their strength is small. Concave arcs are adopted in the shape of the left and right hand grips, and concave bodies are also adopted on the back side to the center, which is convenient to grasp and should not slide off under stress. Sales of more than 400,000 units in two years.