Blitz bounce! If there's one word I had to describe this game it would definitely be "satisfying," especially given the visual and audio effects put into the ball serves/returns. I do like how this is structured as a puzzle game, though admittingly my monkey brain sits there for longer than most trying to find the most efficient solution my first time through. I have no major complaints of this game, and the artsyle does fit the futuristic aesthetic you went for!
The hitbox on some returns definitely felt a bit strange at times, I found myself trying to time my returns in ways that were probably not possible; after getting used to it, I found my stride alright! It might've been a bit misleading to start the animation with an overhead swing (given, I don't think you can hit balls back coming from overhead), but some kind of HUD element may have been beneficial.
Otherwise, nicely done!