Making a first time in jam is really bold, so congratulations! I have a lot of comments to do:
The controls are not good. The slime slides when you change direction but stops immediately if you just stop pressing, which feels like you didn't know what you wanted. I advise you to look at some tutorials, there are many on platformers that could help you with that.
The camera is not centered on the slime (and maybe the others I am not sure) so when you have to turn around you don't know where you are going. Some games focuses on the left if the character looks at the left side and at the right when he looks at the right side, but even a centered camera is OK for a jam like this.
The bird slides a lot while moving to the left and right but moves very slowly in up and down.
You can't move the fish with W and S but you can with the arrows and with A and D so once again, it feels like you didn't know what you wanted for the controls.
Anyway, starting coding is hard for sure! So keep going and you will improve! :slight_smile: I also advise you look at game conferences like the GDC. Motion Twin made a great talk about the importance of controls and how to make a game satisfying.