That was really cute, I loved it! If this is your first time making a game great!! Better than I even! :)
Here's a little feedback: I loved the song! But it got repetitive after 5 minutes in. The tilesets and overall pixelart were also amazing, although there were stretched pixels everywhere. Try using a resolution that gets multiplied evenly across 1920x1080 or 1280x720 resolutions to avoid having stretched pixels, which specially important when making pixel art games!
I agree with the feedback from the others, would be good to have a level up system to go with the skill tree. But it would be even nicer to have skills that work differently from each other, rather than having them just be different skins. You could also make enemies weak to certain elements, just some ideas.
TLDR cute game, but there could be more game to your game. :)
I hope to see more from you in the future! Keep it up!