This is a very nice little game. It sure does get chaotic, especially after you play a while, and it can be pretty challenging. I also think it was an interesting decision to limit the shield to only face left and right, since that really makes you think about your position more, otherwise you end up in impossible situations. I also really liked the screen shake for when you get hit. It's a really unambiguous way to know you were hit. Really nice work!
P.S: How did you manage to force the game to run at a specific aspect ratio? I've been trying to do the same thing for a while, to no avail. :(