Letters are almost always monsters, but which monsters are in which game is anyone's guess.
The Art of Unix Programming: http://www.catb.org/~esr/writings/taoup/html/
GNU Coding Standards: http://www.gnu.org/prep/standards/standards.html
Standard list of long options: http://www.gnu.org/prep/standards/standards.html#Option-Tabl...
Short options from -a to -z: http://www.catb.org/~esr/writings/taoup/html/ch10s05.html
...so this is the "serious" version of what you're describing.
Years ago I made a high res greyscale version of the drunken bishop:
https://raw.githubusercontent.com/justintrupiano/RSA-Randoma...
Forgive the 6 year-ago-me Processing code.
It used an increase in the color value instead of iterating through characters like the original.
But yes, it's unfortunate that Drunken Bishop provides different amounts of protection for bits in different locations. Ideally the protection would be equal among all the bits.