The sprites are very readable and recognizable. The ship is nice and responsive. I found the very repetitive sound effects to be annoying, but I mean that's what this sort of game had in the 80s, right? I like the idea of your health and your shots being tied to the same thing. However, the enemies' basic patterns of movement meant I could mostly just avoid them instead of having to take careful, thought out shots. It should be a serous decision whether or not to take a shot. I'm not sure how you would manipulate the game and the player so that is the result, but perhaps homing enemies, homing missiles, or areas where you will have to sustain some damage in order to pass?
In any case, great job! You should be proud of yourself.