I have no experience with rolling ball games. I tried it out cuz the girl is cute - shame you don't really get to see much of her.
I found levels to be difficult enough even without enemies. I was not able to complete a single level.
My best attempt was pic related:
I watched your video just now, and I understand what you are doing, but I ma not skilled enough. I think maybe more easier level to help ease players into the game would be helpful.
Also when I kept dying over and over, I wish restarts were quicker, but I guess that is not something that is a problem later on when you get good.
I would feel more like pushing through harder sections if I had unlimited lives and checkpoints, but I understand that might not be the game you are going for.
As for the tutorial, I think one thing you did not consider is how when you explain the spacebar attack, players might not have enough charge to use it at the time, which can lead to some confusion.