This is a brain-training game in which you memorize the answers to simple calculation problems that appear one after another, and answer N (number of backs) later.At first, it starts with a normal 3 back, and if the response rate is 80% or more, it will be ranked up, and if it is 60% or less, it will be ranked down.Aim for the highest rank.This app is based on the "N-back task".N-back tasks are said to train working memory.This app is recommended for those who want to train their brain.