Great start
I just bought the addition and subtraction app. I'm going to start teaching borrowing this week and this will be a really nice visual for my students. I've been sitting playing with the app for a few minutes now and a few things I think would make this app even better would be... 1. If you drag a one cube into tens or hundreds spot on the grid it should reject the move 2. When the longs and hundreds split into ones cubes, it would be nice if they spread out instead of splitting on top of each other. With that said, I'm excited to use the app this week!