Nice game! You made great use of the small resolution that was available. The game looks amazing!
It is a bit frustrating that you have to start over from the very beginning every time you die. Especially because sometimes there was an enemy right at the start of a section, which made it very hard to avoid the damage the first time you play the game.
The powerup's are nice, however I do not quite understand what the increased gun power does. It would also be nice if there were some more unique upgrades instead of just stat upgrades.
The sound effects are also great!
All in all a very solid game!