I liked the concept but I found the game had a couple of annoying issues.
1. The clickable area around the number needs to be a little bigger. I am using a HTC One M7 and it often wouldn't register the clicks.
2. After this first game, a full screen ad popped up and that really annoyed me. I don't mind the banner ads at the bottom, but full screen ads are VERY, VERY annoying.