Interesting… I started cooking up a hex cypher code mainly because codes were on my mind and I was unable to access the chans, today.
There are several rules the mechanism could use, and they could be altered between messages or even in the middle of a message using typography.
You start with a hex array of seven arranged in a star pattern. Each side of each hex represents a character. Once the orientation has been communicated, several methods exist for identifying a character. A number can identify a hex cell and then another number represent clockwise rotation of the cell…. Then reference a letter across from a given position (or directly referenced letter, assuming it logically resolves to an exclusion of other interprets).
Numbers would never be larger than 7 in the first set of three characters, the second should never be greater than a single hex character, and the last should never be a letter. An initiation string should exist as well as a set of reference markers so that we know what numbers are encoded to what positions.
More complex rules would not likely be in play until after we have demonstrated competency of the basics.
Kind of a bit of a spitball of a cypher structure. But I was bored and was thinking about webs, winding, and a practical cypher I could use for another project I have going.