It seems like a pretty fun game.
Echoing what the others have said, I'd recommend you make the sensitivity the highest by default. Music added to that makes the game more intense.
Score and Time are a bit hard to see on the dark background, maybe try yellow and white?
I don't play shump that much so I'm not sure of a few things.
- Bullets do damage to your ship from the front almost always. From the side, once in a while. Is that normal?
- Your ship can outrun its own bullets if you push up arrow on high sensitivity.
- How do you activate the bombs?
- Can you make percentage colour change so 100% = Green >> 10% Red? Can it blink or pulse?