We haven't used it on Ipad, but the regular version is not a curriculum. It doesn't really offer instruction. It gives problems, and if the child gets the problem wrong they can click on the "explain" button to see how the problem is solved. For me, that doesn't get enough into the "why" of the math, which I consider very important.

We used it as a stopgap in elementary, as no appropriate work was otherwise available. It let DS blow through a lot of content too quickly, in my opinion.