I almost didn't buy this because the only two ratings are negative, but I decided to go with it rather than the higher rated similar app because this one includes thousands cubes and the other one doesn't. Now that I've got it, I don't see what the problem is, and I can only assume the negative ratings are from competing developers since there are no reviews explaining the negative ratings. This app is simple, but it does what it says it does. I'd like it even more if there were a more graphic representation of the regrouping process.