DragonBox Algebra has a similar concept but gamified. It has a cool progression: you get a new "power" each chapter, like factoring or negating. And it starts out with monster cards then gradually transitions to "x" and numerals. My kids have loved it, but it's hard to tell how much they learn when you can only make legal moves. When my older one learned the basic rules of algebraic manipulation and went back to it, it worked great at giving him a visual model to follow.

That said, the game doesn't let you do arbitrary equations, so you cap out when you beat the game. Excited to try this app out!