Cool little game!
I liked the idea of having the scaling be limited to a certain number of uses, it can add a lot more to a puzzles complexity by having to think about how many times you need to use certain scales, especially when have to divide out your uses throughout the different colors.
I think it is interesting to have the different types of objects only scale specific ways, rather than being more flexible. This likely makes it easier to create some specific level design ideas, but it can also be a bit of a two sided blade of also making the solutions to a level basically a exact specific sequence of inputs. It is a hard design to avoid doing, I know I've often done it before within the past, I even named an entire game off of it.
But, with that, I think it could be nice to see some more objects that can be scaled (or now outside of the theme, maybe interacted with in some other way) Maybe one that will always follow the specific color that was pressed, either going up / down or left / right. Or ones that are "locked" so they can only be scaled in one direction. There is a lot of room to have new ideas here!
Having mouse controls for a game that doesn't incorporate the cursor is a bit strange, I think some key bindings to increase the scale of objects would go a long way.
The player also can't seem to jump when they aren't fully on the ground, which can lead to some behavior where the player would want to jump near a ledge but can't. I'd look into developing coyote time also to fix issues like this, but I can also see how you didn't want the player to possibly scale walls that have the red scale objects on them by just jumping on the small part of it, so if that was the design intention I see its purpose.
Having text most of the levels definitely gave them more character, and I wish they were present in every level, especially in ones where you introduce new mechanics. It was also cool to see rooms be connected within the last level, and I think having that for the rest of the game could add a little bit of charm to the overall progress.
I liked the art style, it was a unique look for the game and it fit it well!
Nice job!