Reply To: Let’s talk about the Playfair cipher
@Puzzling_Pelican one idea for how the grid could change during encryption: you could use a 3×3×3 cube “grid” (27 letter alphabet), using sensible 3D versions of the playfair rules, then use Rubik’s cube style rules for updating the grid. If two letters are coplanar, rotate that plane by τ/4 clockwise/anticlockwise (depending on which way round the letters occur).
Updating the grid reminds me of the rather cute idea of the Hutton cipher variation on the Vigenere. Harry