It has very nice atmosphere and already feels like a finished steam game. There were some major bugs and exploits , the biggest one was box juggling. You can watch the video to see it and the others.
I really liked the puzzles and extra content but last one was too cumbersome and physics based games have some jankiness into them. If reaching the boxes somewhat easier and more recoverable the gameplay would improved a lot. Maybe some magnet type thing let you recover your last box? I am not sure what can be done without breaking current level layout.
Also is moving boxes between rooms is wanted or unwanted? I feel like sometimes you can just cheat some rooms by using other boxes from other rooms but sometimes it feels mandatory.
Overall very nice game and I recommend everyone at least play until you find 1 secret.