I like the little cutscene at the beginning to introduce the story!
The slimes feel a bit slippery but I'm guessing that's intentional! I didn't realise at first it was just arrow keys, maybe enable wasd as well as a lot of people are used to that? I think maybe also have some hints to say what the controls are, and how you can e.g. select multiple slimes.
I like the puzzle design, and sound effects. Well done :)