"Anything really needs changing?"
Well, you could fix the explosion sprites so that they get dark enough at the edges so you don't see a hard edge in the game. The colorsful explosion, and the ship's thrust both display this issue.
The health window doesn't have a black background like I think you meant it to, it's dark gray.
And you might consider adding a subtle parralax layer above the stars of some blue and red space dust, closer to the camera so it moves by more slowly than the stars and thus appears to be closer.
Well, you could fix the explosion sprites so that they get dark enough at the edges so you don't see a hard edge in the game. The colorsful explosion, and the ship's thrust both display this issue.
The health window doesn't have a black background like I think you meant it to, it's dark gray.
And you might consider adding a subtle parralax layer above the stars of some blue and red space dust, closer to the camera so it moves by more slowly than the stars and thus appears to be closer.