For simple sharing without giving it away, what about a RotN where N starts at an arbitrary value (13, for example) but increments for each successive character

For simple sharing without giving it away, what about a RotN where N starts at an arbitrary value (13, for example) but increments for each successive character? ALPHA becomes NZEXR This way, repeats become opaque. Seems clear enough to share in the clear where _breaking_ the cipher isn't a big concern, just immediately recognizing the answer or patterns in it, is.