The presentation is great, and I like that you integrated a story into it, but I'm really not a big fan of the way the physics in this game work... It is VERY jarring that your jump and movement are super fast, but your attack locks you out of ALL movement for over a second. I also somehow skipped the second level? After I beat the slime, I think I pressed the attack button while it was loading, and then I just went on to the monkey boss.
I feel like it would've worked better if you, say, had to charge your attack by holding the button (while still being able to move) and let go to do an attack (which would lock you out of moving for a while still). That, and making the jump/movement less extreme, would make the game flow a lot better imo.
A solid and well-polished foundation though!