Graphics are great, and the music in the title and restart screens is also really nice. I might just be bad at it, but I couldn't make it to the boss (The most I got to was round 2), but it was still really fun. :D
Some (potentially useful) advice: The controls were pretty delayed, which makes me think you may have used addForce() or something. I'd look into using Rigidbody2D.movePosition(), because it doesn't change the object's velocity, allowing it to stop as soon as the controls are released, rather than needing to slow down. It's like translate, but it maintains physics. If you didn't use addForce, ignore what I said, and maybe look into finding, and potentially fixing up anything in your code making it delayed (for the next time you do this type of player motion in a 2d game).
This isn't to say that the whole game is bad just because the player movement feels a bit slippery. That would be stupid. Its really nicely made, but I figured I point out something that might help you with future games you make, and something that could be a mistake I made many times. Overall, it's really good and I enjoyed it. Good work! : )