I'm going to say this and you've probably heard your fill from other reviewers, so read away as you wish.
I assume you're an aspiring indie developer with a vision and a passion to create fun games, so I'll judge your game with my assumption.
First of all, using a game template (stencyl) (Gamemaker Studio) for your beginning stages is quite nice to understand how powerful coding is. If it works for you and your game gets popular, by all means continue using it.
Secondly, controls and mechanics. Simple platformer game, simple controls. Easy to learn, not enough to pay attention to. Mechanics: Jump, run, shoot. That's just fine. Nothing unique though. Very similar to a mario game. Run and jump, avoid and/or destroy enemies to progress. Princess is in another castle, The princess is a chicken in this game, essentially.
I love how you added powerups. I was excited to see the two decisions I could make in your game.
1. Be strategic and utilize the environment to progress.
2. Farm enemies and upgrade your way to the top.
It's late here and I have to go to wake up early, so I hope I've made a point here that interested you to at least gain some good feedback and/or learn something new about your game and even yourself, depending at how deep you look at it, I guess. ^_^
P.S. Cute character. I would love to see him everywhere and might even buy a plushie of him if you ever create a physical copy.
The game was not entirely unique, but that's quite alright! You have to hear straight feedback to get better! Good luck with being a game designer if this is your goal/intent.
I have faith in you so i followed you too. :)