Impressive technology for age group. How did they do it was my kid first question. However, be careful replacing batteries because the compartment screw gets damaged easily. Now I can not get it off. That's why it is 3 stars.
Really liked this product and couldn't find it is stores. Pricey, and doesn't automatically "turn off" so will probably have to buy a lot of watch/ calculator batteries if the kids don't understand. But nice and compact.