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 :)