Super, super cute art style, and a great concept!
The gameplay is super satisfying!
There are a couple clarity issues, times when I didn't understand why green slimes weren't making other slimes when I smooshed em together and things like that, also I'd have loved an indicator when I hovered over a slime so I didn't accidentally ever /not/ grab one, but those are just some small polish details!
Overall, a really really great entry. Nice work!