This app is devised so that you can train mental arithmetic while having fun as a game. Mental arithmetic does not improve immediately. If you are not good at mental arithmetic, please don't give up immediately and use it for your daily training. I have prepared a short video so please use it. Video size: 2.1MB 1. About the calculation formula Addition and subtraction can be selected in this game. Furthermore, the number of numbers to be calculated will increase every 10 questions. As the numbe