I don't think it was until I started learning programming in school and fully understood what "debugging" meant that it started to make sense what the purpose w

I don't think it was until I started learning programming in school and fully understood what "debugging" meant that it started to make sense what the purpose was of the "debug mode" that video game strategy guides would show me how to unlock. I thought it was there for the players to find and entertain themselves, like cheat codes. Only later did I realize that stuff like model viewer, events viewer, stage select, etc. was all stuff developed for/by the QA team.