DragonBox is an educational game that teaches Math fundamentals fun and interesting. There are 5 learning apps for learning Math in total, including algebra and geometry. All 5 games in the app require up-front payment but don't have in-app purchases charges.
When math teacher Jean-Baptiste Huynh noticed that many of his young and enthusiastic students, although otherwise intelligent, struggled with algebra, he figured there was a problem with the way the subject was taught, and not with the students themselves. Because of this, he decided to found his own educational software company, We Want To Know, together with Patrick Marchal, Ph.d in cognitive science.