I like the feels of this game, the color, the music, atmosphere.   I got the first puzzle so I feel good now

So, I don't like these types of games, and I while I don't think you should necessarily follow my opinion if you make something like this again (better to listen to the opinions of those who like the genre), I think you've made a very good example what bugs me about these types of "puzzles."

I got to the second room, did the first steps and came across this result, which I am specifically writing this way to avoid spoilers but still give some indication of what's gone wrong:

D - 7 = 6
6 - E = F8
5 - 0 = 5
2 - D = F5

I imagine the clamping methods usually used with the context in question could help, but only if an order were provided, as merely assuming a consistent order would still leave 2 solutions. There's also the option of interpreting casually, which I did. It didn't work. Even if it had, I still would've had to assume a hex order, which still would leave 4 solutions. Neither normal reading order, nor an arbitrary meaning for "one" worked, regardless of casual assumption for starting with 1 or the more sensible order within the context (starting with 0). With that many possibilities, trying to guess what you were thinking is rather tiring.

Also, having to use arrows to enter in the codes doesn't help in the slightest.