The game looks very good. It's a little annoying that the pen is in front of the tutorial instructions, though. Moreover, the notebook itself hides quite a lot of the screen! It also feels a little weird that we need to quickly react in such a small area of the screen but need to closely look at the ball to make sure we do it at the right time!
The idea is fun and interesting, I think there is a lot potential if you fix the UX issues!