Cool game! I liked it so far. I'm not quite sure what to do in level 6, I will return to it tomorrow and try to beat it. Also jumping sometimes feels hard because as far as I can tell there's no coyote time.
The game window seems to bug out on certain resolutions and on my computer a bit of the screen gets cut off. For example in the cutscene I didn't see text and was wondering why there were some random images with no sound and no explanation. You may be able to replicate this bug with Ctrl+Mouse Wheel on the game page (you need to click somewhere outside the game window first). You might want to experiment with Mode and Aspect in Display->Window->Stretch in your project settings.
That's also what I said for a different submission here, but to keep the art cohesive you could try to avoid having mixels and have all the art use same pixel sizes. I found it helpful to design various sprites in a single file first to ensure right sizes, detail levels and overall style consistecy. Then you can split them up into separate files. For example when you're designing a door sprite, you can copy the player sprite into the canvas, so you know how tall the door needs to be. That way you won't have to scale the door sprite later in the engine and will avoid mixels.
Sorry for the wall of text, sometimes I'm little too verbose lmao