Great job with this!
What I Liked:
Loved the aesthetic. The music & graphics fit well together and made for a good atmosphere.
I liked the bit of humor (the sound effects were funny and telling you "You Suck" after losing a few points was good)
The particle effects on the ball and the trail behind it looked great.
I think the extra mode was pretty cool. I think the "powerups" created some more interesting gameplay.
I'm really curious how you did the AI. How hard was it? I'd imagine it was a bit tricky to make the computer challenging but not perfect? What did you do to ramp up the difficulty?
What I Would Like to See:
I found that if I positioned myself at just the right position at the start of each point, the ball would always hit off my side and go off to the side, giving the computer a hard time getting to it and giving me an easy point. Not sure the best way to prevent the player from these easy points (maybe vary the initial trajectory at the start of each point?).
Awesome stuff, well done!