Oh boy; this brings me back! I grew up in the era of Flash, so I've probably played fifty games similar to this one over the course of my childhood. The one that comes to mind more than the others was called "Scary Maze Game," I think. I mean, this is pretty much a new and improved version of that without the jump scare, so I'm not complaining. Nevertheless, I do have a few suggestions, which you by no means need to take.
First and foremost, I think that a bit more explanation within the game would really elevate this. It doesn't even need to be seamlessly implemented; just telling the player what to do directly is better than nothing. That said, there are definitely clever ways to explain things without directly explaining them, and you actually used one when you made that safe screen that just allows the player to find the goal on their own. A bit more explanation would have certainly been welcomed though.
Next, I'll say that the rooms never really felt like a maze. I always knew exactly where to go and never felt lost. Maybe adding multiple, branching pathways with several dead ends would help with this. Or maybe make each room start dark, and have the player "map" it by walking around. That might be really cool.
I'd also add that the game mechanics seemed relatively inconsistent. Sometimes we needed to push a box toward the goal? But the goal looks almost identical to the goal where we don't need to push a box toward it. How was that communicated to the player? It just doesn't seem to make sense within the game world. Maybe if you made the "box goals" blue or something it and the "regular" goals green would make more sense? It would at least be distinct. I don't know, though. As far as puzzles go it just doesn't seem to stimulate the mind. Maybe if the boxes could instead be used to hold down buttons that opened doors! Now we have a puzzle!
Finally, I think that maybe having some simple sound effects would really take this game up a notch. As is, there's not too much feedback when a player does something. I mean, the character moves, but just a simple blip when the player dies, or a pushing sound when the box moves would make everything soooo much more satisfying. Those are just examples, but there are several places where this would be good, I think. There's some great free software (maybe try bfxr) that can generate all the sounds you need in a few minutes.
Anyway, thank you so much for the game! I had an absolute blast playing it, and I really hope you add more content! Please let me know if you do, as I'd love to see where you take this!