You should have the option to adjust the time. Like no time limit, slow, & fast. You should also have it set for different ages, and give hints for example:
17x18=?
17 Hint 1: 7x8=56
X18 5
โโ- 17
X18
โโ-
6
Or however you do it, and if you add the hints and slowing the time you should add categories for fractions and decimals. Other than that, this app is ok.