Great game :>
The graphics are really good, both in execution and especially in the monochrome style. If i want to be nitpicky then the background could have used a bit more motion to seem more alive.
The gameplay is where the game shines though. By combination the sfx (mostly the UFO hit sound) and the graphical effects, like the ball smearing, every hit is satisfying and has great punch to it. I never felt like i had good control when curving the ball, which paradoxicly made it feel smoother.
The music, while in principle good and relaxing, is in my opinion bogged down by having too much room, too much reverb, which makes it really unfocused and distracting from the other better qualities.