Mental arithmetic training application.
If you win 10 games in a row, you will go to the next level.
level1 : 2-1, 5-1, ...
level2 : 3-2, 7-2, ...
level3 : 1-3, 6-3, ...
...
level9 : Review Questions
level10 : 15-3, 17-5,...
In Japan, 6-7 years old (1st grade)