Awesome art style, should be really cool when its done. Really buggy though, even for a demo this could've had just a bit more time in the oven. Some bugs that kinda bothered me were the wall clipping ones when you jump and that the flies aren't at the character's height so you can't shoot them standing plus when you jump, your window to hit them is incredibly small.
One interesting bug I found is that if you jump on a spring (instead of walking into it, which works as intended), you go right through it and it sometimes makes you next jump extra high even if you don't jump off the spring.
Anyway, keep it up.