This app is absolutely amazing. At first, I discarded it. I was trying to find learning apps for my five year old, to get him to like the computer (instead of just his iPad). I downloaded this, couldn’t figure out how to help him play it, and bought him other things. Then one day he decided to start playing on his own. And in I walk one day, and he is isolating the ‘x,’ cancelling out like values on the top and bottom of the fraction sign, and canceling out ‘a’ and ‘-a.’ I sat down and watched. And I saw the genius of the app. It uses graphics - negative and positive versions of the same graphic. And it has two screens - to represent the two sides of the equation. It slowly increases in difficulty, and has the child generalize between cancelling out a black and white alligator, to cancelling out a positive and negative a.