I liked the aesthetic and the theme is well executed, I feel. If this is your first game, as you said, I'd say it's a very strong entry into the world of game dev!
The controls are good, but the slow sticking on walls is not something I appreciated. It would make sense if your character could wall jump, which I don't believe is possible in this game, but without the wall jump this sticking just gets in my way. I'd rather have the character slide against the wall without slowing down.
I did not like how the pressure buttons were implemented. I'd just make them activate whenever the player/box is above them, without them being solid, otherwise pushing the box on top of the buttons gets a little finicky.
This is merely my opinion: The "void" level I think is a bit too big of a difficulty spike! Having to manage the spikes, platforms, your bar and the void expanding was not fun for me. But some may disagree. And the maze level afterwards felt a little boring, but I just tend to dislike maze levels in general so it's just my opinion.
I'd also make the text parts either faster, or have a key to make all the text show. I like to read everything, so I wouldn't skip it, but it is a bit too slow for me and so I have to wait for the text to appear.
That final part with the big red square was a clever twist. And it is a good incentive to make the player go through everything again to try to see if there is an alternate ending! Which I did not do, at least not yet haha. Is there anything you can do in the red room at the end except the obvious? (Hard to talk about this without spoiling!)
I don't know if this was intentional, but I thought that the "begin level" and "end level" walls not being real was a really clever detail. Also the text in the final red room!
Great game, I enjoyed it a lot.