Hey, cute platformer. I like the overall look of the game, but there were some things that were bugging me.
I think generally for pixel art games you want to keep the pixels all the same size. The cat, platforms, and stars all mostly have the same pixel size (Except for some islands that are scaled up). The background and the checkpoint flag have very different sizes.
Another thing that was that the outlines were not super consistent. For example, on two frames of the cat idle animation there's some stray pixels on the bottom of the eyes. Not a huge deal for a jam game, figured I'd mention it anyway!
As far as gameplay goes, I agree with Ran that it gets a bit frustrating after the first checkpoint. There's also a bit of inconsistency with how the character behaves on moving platforms. It's pretty jittery on the up/down ones, and on one of the left/right platforms it wasn't moving my character along with it.