Writing an NES game for my senior project helped me understand what exactly the minus 1 world was.<p>My Game had 4 levels, and if you go to the exit of the 4th level, you enter the secret, 5th level. Except it’s not a secret 5th level. It’s the answer to the question “what happens when you try to go to the next level and there is no next level?” It turns out you get a level built out of whatever is written in the ROM address.