Mmmm for me the game in the church had an easy solution. You could think about it or just try guessing. Everytime you guess it, the option disappears and when you fail it resets . So there's a very limited number of combinations.
I'm not talking about the difficulty of the solution/player, but the gameplay mechanics for the puzzle that you have to code.
For example, I've seen a lot of indie devs get burnt out trying to add things like a basic combat system, or a minigame puzzle mechanic, point-and-click mechanics, etc. The time stretches on of them learning, redoing, etc and they lose motivation in their game.
My recommendation is to keep it similar to the church puzzle - dialogue clues and a choice tree. A lot of devs get caught up in trying to add new and unique mechanics and it burns them out because its more work then expected.
Ah no don't worry about that :) In any case I have a lot of experience on computer programming (my real work is related to that) :) I started with my spectrum long long time ago. I'm and old pervert hahaha. Not planning to do complicated things. Mostly flavor things. So don't worry about expending lot of time on that :)