great job! you provide a cozy and charming experience.
the world is field fun secrets and interaction to keep the player engage, the platforming is a little standard but I am sure that with more polish and platforming mechanics introduced later could be much better. (not that this is a bad starting point its actually decent, I had fun)
controls:
-input jump buffer is to small or none existing (jump input doesn't save for few milliseconds if you are not on the ground yet)
-*jump height isn't different depending on how long the jump button is held.
(just the stuff you see in every how to make a good platformer controller tutorial)
*if you need help implementing this (I found it takes a lot of time to get right) I could send you code I used to achieve this
art:
-it might be temporary but the backgrounds are drawn on a much smaller size (or maybe aren't detailed enough) and than the sprites looks off in contras with the background.
-shadows and lighting in cutscenes is weird, cartoons don't have real time lighting
-chunk fish (i think) with too much shade on them looks like a part of the background
nitpicks:
-the chunk fish is great, the sound the animation its very polished in contrast to the main character the slime who for some reason doesn't have sound effects (weird priorities in the sound design)
-some animation for the main character are missing: landing (i would also add some more slime particles here), on ground and holding move against wall (should squish against the wall)
-for some reason the speakers dialog is skippable (why? you don't have to read it and I accidentally skipped it)