For my game "Revisiting the Exit" from last years contest, control codes were used extensively just to squeeze it into the PUR-120 category and for my code explanation I took screenshots with the code, explained what the standard command was for the most part (don't know why I didn't have it for the SYMBOL data though), and just had comments following that. I explained below how the Control Codes were obtained via keyboard, as well as the condensed characters through the use of CHR$() and Cursor Copy. Magazines wouldn't have appreciated such a listing back in the day due to the control codes, though for this contest every keystroke matters.
Cheers, Ross.