Thanks for the feedback !
I tried my best to introduce them in the earlier levels, but it can definitely use more levels in the beginning to familiarize the player more with the box, before playing actual puzzles with it.
I'm finishing the game how I imagined it, with a better difficulty curve, level selector on the left when you start (only accessible if you know how to open that door, by having solved a couple of puzzles first), and just some general polishing, and hope that will make it more accessible to anyone !
Thanks for playing and glad you had a fun challenge, which was the intention !