Hello Spirits, saw your post on the forum, and since I like to give feedbacks, here I am!
Your game is really nice: the idea is simple and it seems well polished. I think you could make the gameplay more interesting, maybe by adding more variety to it, or making the player faster (as Steven pointed out). I believe it would make the game more fun, but either way, given the time limit of the jam your entry is pretty solid. Shooting diagonally would be nice, as well.
Also, I believe I found a bug: when I got to 3 health I believe, the game closed by itself: was not able to reproduce it though, so I can't say a lot more about this "bug".
Anyway, yours is a really nice game :)