These old games password systems analysis are always so entertaining and interesting to see... just like a glimpse onto the limitations that were faced by 8-bit console gamedevs in the early days, and the very clever solutions they came up with.

There's this Youtube creator called Bisqwit who has a complete series on cracking old videogame passwords:

* Season 1: https://www.youtube.com/playlist?list=PLzLzYGEbdY5nEFQsxzFan...

* Season 2: https://www.youtube.com/playlist?list=PLzLzYGEbdY5mmad-FKPIl...