This game is a masterpiece.
The developers are awesome and I love them.
My daughter is 4 and a half, I taught her numbers and to sum or subtract big numbers, but since we played this she learnt how to solve equations, what negative numbers are.
The games make algebra fun and easy.
The bad side: stealth algebra should be sold also to adults, I know many people who'd benefit from such an app!
Whatever age you are, get this game.