First and foremost, the art is solid. The title screen in particular feels beautiful and professional. And the story about a slime getting out with its friend is pretty cute.
I know I'm not the first person to say this, but the final level is unintuitive. I was moments away from giving up on it completely, especially when failure meant restarting from the beginning. Eventually, I thought to try sending one of the bigger slimes into the final gate so I had more to work with and was able to beat the game. But the game doesn't teaches you to consider slime size beforehand, so it feels arbitrary in practice.
Even when I figured that out, my setup still required me to avoid at least one bat in the final level. But until that point, bats were a positive object that enabled the player to solve the puzzles. I felt like the game was breaking the rules by making the last one into an obstacle.
Also, I don't think this game fits the theme. I take it you took it into account because it's on the title screen. The gameplay revolves around dividing into multiple slimes, and the last level requires me to put the biggest slime I got through the door. The mechanics imply "more is more" instead of what was originally intended.
Still, I did enjoy my time enough to see the game through to the end despite my initial confusion. Finishing a jam entry is an accomplishment in-and-of-itself, too. Congrats on seeing the project through the end and thank you for the game.