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。