I would like to be able to hit the ball with space bar instead of S or down arrow keys... Using the same finger to jump and to hit the ball feels awkward.
I would suggest the speed being not something random that makes some squares almost stay still but something that keeps increasing with every square that pops out. That way the game will get harder and the player with not be bored because the game being always the same.
2/5 because you've actually made a game; if you add this feature, I'll give you a 3/5.
The green dot reveals for a little time the other circles.
I guess that this game would be better if you make levels harder because waiting till level 20 to get it harder enough to be a proper challenge is boring. 4/5
There are some things that you need to change... First, the hit area, don't know if it's the enemies area or the player area, is way too big to play fine.
Then, you should add a score or some kind of point system that shows the performance of the player. 2/5
Look! I have one minute of delay between the arrow and the note! The game is so funny now... Fix that please, I do not have any kind of lag, the songs just start some seconds after the arrows start moving.