Look at *differences* between words rather than at the words themselves?

[radapox]

Hello radapox,
I like your approach because basically it's easy. Something like this is feasible for a writer of the early 15th century. I myself tend to make things too complicated and end up mostly in dead ends

Thanks! I'm not suggesting that I'm on the right track or that this would be the only underlying principle to the cipher, but I thought it's an interesting idea to consider.