Some classic games would generate a "code" you could enter to resume the game, all codes would deterministically map to some game state. Ghostbusters for Sega

Some classic games would generate a "code" you could enter to resume the game, all codes would deterministically map to some game state. Ghostbusters for Sega Master System did this. One day I had a typo in my code and ended up with obscene millions of dollars. I always wanted to go back and RE that game's code generation algorithm...