This is the best children's app I have ever seen. Not only does it teach mathematical concepts in a fun way, it teaches how to construct objects and form proofs in a fun way. If your kid loves gaining "new powers" and taking on "tough enemies and bosses", your kid will love this app. (The rest is for geometry buffs and nerds: it views construction postulates as powers; as you advance you concatenate these powers and get new powers. It doesn't touch the 5th postulate in Euclid, but who can blame it for leaving that one alone! Each object needs to be constructed from given objects in a way, but in a way they are already there: you add new colors to existing lines and angles. This makes one feel as if construction matters (QEF is not QED) but doesn't reduce the view to something like Brower's intuitionism, since the yet to be constructed objects are still "there" before you color them in.)