Math drills can be boring, even apps that try to gamify the experience. In this iOS/Android mobile app aimed at 6-10 year olds students play a tower defense game where they energize towers by solving math drills. Aliens have landed and you must stop them by using their own technology against them.
Math Defense uses a Freemium pricing model. The addition pack is free, but subtraction, multiplication, and division tables must be purchased separately as In App Purchases.