Cute game! I really dig the art style and little touches like the fade to black when you start / die (though curiously I could still move after i died...). Also, the presentation is nice with the matched color scheme on this page, animated screenshot and stuff. I also like the mechanic where you can get health back by killing ghosts.
I have some critiques, though. The camera was lacking -- I felt like I was fighting with it for a lot of the game, especially the part where you jump back and forth to get the silver (?) key. At that part, it was honestly pretty nauseating. Also, I was getting frustrated with the fact that you can slide off the corners of blocks. That felt kind of out of place in a platform game.
Another little thing, the controls felt really unintuitive to me. I think WASD, N and M or something (or at least the option) would have been better. I found myself forgetting which button was jump and which was shoot.
Finally, a little tip, I think you could make the game feel "juicier" by adding some squash and squeeze on the ghosts when you hit them so that it feels a little better to play.
I hope this feedback was helpful!