I love the visuals and the sound effects here.
However, I think you need to tweak the design aspect and how enemies should be implemented a little more. At one point I couldn't move at all because the enemies that moved from side to side kept swarming me. I didn't see any more power-ups after a minute into the game. So once I got damaged I was back to shooting single shots for the rest of it.
Also, if the game requires a game-pad in order to play, then let your players know on the title screen once they launched it. Along with telling them what buttons to push.