Mental arithmetic training application.
If you win 10 games in a row, you will go to the next level.
level1 : 10x3, 10x5, ...
level2 : 11x6, 11x4, ...
level3 : 12x7, 12x2, ...
...
level10 : 19x4, 19x8, ...
In Japan, 8-9 years old (3rd grade)