I'm completely shocked- I managed to beat this after a half hour of figuring out what the "rules" were. Very fun little game, also infuriating but I love a challenge. Made me feel glad that I'm stubborn. Great work!
Difficulty seems fair- if it were any harder, I would have given up, but any easier defeats the point. It's not supposed to be easy.
Also, could not figure out where or when to enter the code. Going to try one more place but am having no luck with that.