Love the pixel art! The rocks, hat, character, and animations look great. I wouldn't change a thing. I like the green ghosting effect too when the player jumps. I think the main gameplay mechanic is excellent as well. From my personal experience, I was never able to recall my hat. Could be a bug to look into, unless I was doing something wrong.
Just a small suggestion, on your ground tile, you could delete the area I highlighted in green, and it might give the rocks more of a rocky look. It's just an idea. I'm only mentioning it because I think your game has a lot of polish and could easily be a full game. So, I'm just offering some ideas that could help. But it looks fine either way.
