Mental arithmetic training application.
If you win 10 games in a row, you will go to the next level.
level1 : 12-10, 15-10, ...
level2 : 10-2, 10-7, ...
level3 : 11-3, 11-6, ...
...
level9 : 17-8, 18-9,...
level10 : Review Questions
In Japan, 6-7 years old (1st grade)