Interesting idea! The game is easy to pick up and understand, but hard to master (for some reason, I am really bad with looping borders!). The presentation and the music are fitting. The thruster sound effect is a bit too dominant and gets annoying after a while.
I know it's scope creep, but an occasional upgrade would keep me playing longer. I lost all my asteroids pretty fast, and starting over with 0 felt punishing.
Also, I would add an arrow as you get bigger; the ship was so small, and I was not sure where I was pointing in the later stages of the game.
Overall, a great submission! Good job!