That would possibly work for 3D first person games that do some kind of frustum culling of game data, which is an interesting idea. But Nebulous is a 2D top-down game so its not really applicable.

That said, I vaguely remember a similar sounding technique used in the Diablo 2 map hacks of yore. I think you could simulate your character moving around somehow (locally) to reveal the entire map. There were other techniques as well.

For something more along the lines of "An intermediate's guide to game hacking techniques" look up diablo 2 hack implementations. In my unprofessional opinion that is the most hacked multiplayer game of all time in terms of variety and creativity. Examples: https://www.reddit.com/r/Diablo/comments/24h8gh/how_were_peo...

Edit - oh just remembered a fun D2 anecdote: someone was able to memory-inject a keylogger on my machine and steal my password when I attempted to pick up an item he had dropped in the game. Not fun at the time!