The heart of this game is the 'cracking the code' part. However, the 3d conversations and moving around is really impressive for a 1 week dev effort.
I liked the puzzle - at first I though it was going to be a version of Wordle - and then I got confused.
Changing the cypher substitution as the code was being cracked was a great idea - but in the end it was possible to just cycle through the alphabet on each square until the right letter was found.
Instead you could maybe do something like have the player figure out how many letters change at each square.
So instead of trying to find the letters, you were trying to find what the change (in number of letters).
You could have all the letters filled in at the start with random changes, so when player made a change, all the letters would change from that square onwards. Not sure it that make sense to you.