It's def difficult to make puzzles in games that are difficult enough to be satisfying to solve but not too difficult to cuz players to quit, and that's def a skill that comes with more attempts at making those kinds of puzzles. I tried finding it on my own and after a while I was able to successfully find the code! It's an interesting game in terms of atmosphere that I think would have benefitted a lot from some horror audio.
Also I really think you should look into making a WebGL build, it's very easy to do and is really accessible for players which will allow you to have more people play your game. Here's a short and easy vid on how to implement it I really hope this is helpful!