Here are some rules that you can accept when playing against me. I will accept them back.
Each rule adds a custom symbol:

is null (always not the right symbol)

is void (for the guess, reported results act as if there was nothing in the space corresponding to the void for both guess and code)

is exception (reports

if the space it is on corresponds to a symbol in the code nowhere in the guess,

if doesn't report

and there is a symbol in the code that appears nowhere in the guess, and nothing in all other cases)