First of all, controls are not intuitive. It's not like you can't get used to them (I got), but I haven't seen other games with that control scheme, so better keep to known standards. Also, when rotating when at zero velocity, I could easily lose a lot of fuel, that should be fixed. Bot AI is really decent, they try to hit you, but not endlessly, they don't get bugged. Interaction between you and your enemies is really fun, and if you want to make real game from this, you should focus on that. Maybe adding multiplayer and more interaction could add more to this game.
About balance. For me, it wasn't really hard to get past 30, but it was **too long damn time**. Better increase fuel lost amount, so the 'hard point' is about 10 level.
Music was fine, it didn't make me mad or irritated.
Also, try rating other devs' games too, then more people will be able to rate your game.
I almost forgot. Sounds made by trucks and rockets are absolutely splendid xD