Great curve mechanic, bouncy bullets, and sound design. I think focusing on the sound to expand the world was a great choice and made the game feel good.
I also liked the opening menu that establishes a sort of dangerous experiment world.
In a personal sense I was unable to beat the first level. I hit both the cubes once but was unable to stay focused and defeat them regardless of trying many times. I am an "easiest mode only" game player and am really interested only in story, so perhaps making the game difficult has an audience outside of me.
A final note on the sound design, I liked the enemy cube grunts.