How I Use It
This is a standalone app for addition. I would start to use it for kindergartners when they start to learn addition. Then I would use it for 1st grade to practice their addition skills. It works for centers, students can work on their own, and it works for pairs, so students can help each other out.
When I first tried it, I thought this app was a simple addition app. After using it a second time for more than a few minutes, I am amazed how good this app is! It has multiple ways of solving problems (excellent scaffolding), so it caters to multiple ways of learning. Also, the 2nd round has the number line, so it's more diverse than most math fact apps. I would easily recommend this for K-1 classes.
Also, it doesn't just say "-1 for getting it wrong," it has hints and it gives you steps to solve the problem (2nd try).