Thanks very much for playing the game and I'm really glad you are having fun with it! I need a bit more practice at creating audio in pico 8 before I could put music in the game, at the moment I think it's better that there's no music instead of there being bad music in it! I'm not sure which enemy you're referring to and the shots being impossible to avoid, but for the most part the enemies in most waves appear in the same positions each time, so if you play a few times and learn which enemies appear and when, you can learn where to place your ship to avoid a lot of the shots.
Thanks again for playing the game and leaving feedback, it's really appreciated!