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, ...
level4 : Review Questions
...
level9 : 2+6, 1+8, ...
level10 : Review Questions
In Japan, 6-7 years old (1st grade)