I love the art and the sound effects are hilarious. I like the mechanic of the slimes melding together, but it feels like a lot of other games in this jam. Still, amazing that you built something that feels pretty polished in just 48 hours.
I personally don't like the slimes jumping on each other thing. The slimes are round, so it's not clear that they can stack stably at all, and when you miss the stack, the slimes tend to orbit around each other in a way that looks like they can't be stacked. I would say maybe add a flat surface to the slimes so it's clearer that they can stack on top of each other like that, but also the rolling is so darn cute....
IDK, that's going to have to be a design call that you make. Maybe you just need a simpler level to introduce that? Maybe have the goals kinda in the middle of the screen where you'd stack them instead of on the sides, so it's clear what the end-goal is?