I think it's a very interesting idea with a lot of potential for making great puzzles. I also like the visual style of the game, I think it fits well here.
It took me long but I figured out how to absorb multiple slimes and that you can stack them in one place. The game doesn't really teach you that slimes can stack into a bigger slime. So a better tutorial would be nice. Also, I found some invisible walls and even got out of bounds (I think) once.
Still, it's a nice game! Great job!