This is a really fun game. If you'd expanded it with upgrades and stuff between rounds, it would feel like a really fleshed out game. Unfortunately at the moment it's lifespan is pretty restricted, but in that time it is really fun (my high score was 632). It needs a decent bit of skill to play, making it something I could see myself competing against my friends at.
Edit: One more thing, the sound gets a little annoying when you're spamming a lot, maybe replacing it with a continuous sound that fades in and out depending on whether you're using your thrusters would help?