脳トレ！暗算50問

It's a super simple mental arithmetic game.
There are only two difficulty levels, one is a one-digit problem and the other is two-digit addition, subtraction, and problem.
App features
-Since it does not use difficult Chinese characters, it is easy for children to play.
・ Since simple calculation of addition and subtraction comes out, even for children who want to practice calculation
It is also recommended for elderly people who want to do some brain teaser.
・ If you answer correctly in a row, you will get a high score.
・ There are rankings for each difficulty level, so aim for the top three.