This is gonna sound like a bug report / stream of concessions while I play through the game (really cool game btw):
Is the tutorial just "wow this is very nice"?
Maybe a stronger hint is necessary in a tutorial
Is the 2nd door meant to be just the credits page 3 times? There are stars when you go near the door so it seems like a set of levels
The instructions say the skeleton and ghost become enemies but you can walk on them? Maybe enemy is the wrong term here, maybe moving platform would be better.
Options appear to be in spanish in one screen and then english in another (kudos for supporting multiple languages though)
My mouse cursor disappeared after the 3rd level (maybe cos I'm switching tabs to write this)
I fell through the floor while pushing a crate, don't think this was intentional
The hold R to restart is excessively long. 1/2 second is probably long enough in case of accidental clicks and then it also require lifting off the key so it adds some additional time when you want to quickly restart. Just make restarts instant.
After completing all the levels it says "Defeated" probably a mistake
The tutorial door has 3 stars above it but you only get 1 star after completing it (my OCD dislikes the missing stars)
Definitely the bones of a great puzzle platformer here. The scan lines I can take it or leave it. The pixel art and lighting and presentation are top notch.