In terms of basic game play this is a pretty solid retro feeling platformer

The world felt too big and sparse to me. I spent a lot of time walking without anything interesting happening and then I'd be at a dead end and have to walk back. I think I would have enjoyed this more if about 60% of the empty area and places where it's just fairies drifting around were removed.

I reached an area in the lower left that is maybe supposed to be dark? It was unclear. I stepped through what seemed like it might be a gap in the wall leading to a new section but then fell instead and found a key in a lit area below. By jumping randomly in the dark I managed to get back up to the level above but I could never get out to the initial area or get further to the left past the candlesticks. And then a duck sat on my head? That may have killed me but the darkness was hiding my life meter so I couldn't really tell.

I think you have a good foundation of a game here, the mechanics such as jumping, shooting etc all felt nice and overall it was quite well polished.

My main critique would be the level design. I do really enjoy games where you are free to explore, gather items that help open up new areas etc (Metroidvanias I guess) however I think making the areas so open (and large) didn't work to the games advantage. You could have got so much more out of scaling it down, as an example I dropped off a platform and there were spikes below but I had no idea they were there as they were out of view. Again I think there's a great foundation here it just needs some tweaks and visual queues to give the player a bit more direction. Good job though :) 

Camera moves a little quick which made jumping jarring! Getting through all of the fairies in that one spot felt great. At first I was jumping on them trying to get to a higher area because I noticed they were platforms but when I died I learned what I was doing wrong. Neat little jam!