Extra fees
Decent enough apps that help kids learn addition but don't expect to be able to see why progress your child is making as a to her or parent unless you anty up a ridiculous monthly subscription fee. There is no way to check on your child's progress with math facts unless you pay for their reports. This should be included in the cost of the app. Addition is free but their other apps cost and you can't review any reports unless you pay even more on top of the original app fee.