I like the art, and the map was surprisingly big for a game made in such a short time!
Some issues:
The default window size is too large for smaller monitors (health bar is almost offscreen), webgl's fullscreen is really good so you should just rely on that for screen size.
The optimal strategy is to never shoot. Seems like an oversight, not sure how to fix that one.
It is a little hard to feel like I am making progress as I walk through the game, since there is no score or time.
The platforming is annoying if you fall, if this was supposed to be the main hurdle in the game, then the platforming difficulty should've steadily increased, and there should be more movement options to keep platforming fresh.
Some future ideas:
If you had enough time, I think the background would look great with parallax!
The enemies having complete differences between them would make combat more strategic.
Overall, good concept! #unity gang