Neat idea for a puzzle platformer. I like how you can use the collectible slime for extra jumps. It was also smart to give the slimes a double use for both jumping and defeating enemies. It would be cool to see this expanded on with more uses of the slime and interactions with other mechanics.
I do feel like the last level got a bit boring. It was mainly jumping from platform to platform without much variety and it was too long. Other than that, I enjoyed the game and like the concept. Nice job!