Brain training calculator

Every time the user presses a number key, all number keys disappear and their arrangement changes. Entering numbers can be hectic and requires concentration and patience. Users can exercise their brains and keep themselves busy. ＜モードオン・オフ＞ 隠すモードボタンを押す。 ※普通の電卓に戻る場合は、ボタンを再度押す。