Elemental Arithmetic play online

This software is self study tool for elementary Arithmetic.it has no advertisement.
You can choice below 4 difficulty type question.
1. Basic addition (answer is within 10)
2. Basic subtraction (answer is always plus and 1 digit calc)
3. Addition(increase in digit) (question with 1 digit, but answer is 2 digit)
4. Subtraction(decrease in digit) (question with 2 digit, and answer is 1 digit)
At first, only type 1. if you want to add another difficulty type, open menu and choice you want.
If answer is incorrect, you can see hint. One time, only show square for count, and answer is incorrect again, next hint appear.
When calc type is 1, show square in line. when 2, show square of base number and show cross of subtract number. when 3, show square in line and show support square and line for inclese digit. when 4, like as when 2, but cross start from 10. it's like buy something with 10num coin and change.