64 door hierarchy glitch

64 Door Hierarchy Glitch is a glitch in the original Super Nintendo Entertainment System versions of Final Fantasy IV (known as Final Fantasy II in North America).

There are two types of map/room changes in Final Fantasy IV: "Go" types and "Return" types. "Go" types save the player's location, and "Return" types go back to a saved location. Locations without a clear cut "Go" or "Return" purposes are "Go" types whether coming or going. Outside, the player is at Room Level 0, but every time one enters a room the "Room Level" increments. Each time one exits something, the Room Level will decrement. The glitch can be performed in places where one can continually increment the Room Level.

If the Room Level hits 64 it resets to 0. If the player then uses a "Return" method (by exiting a Return door, or using Warp), they will be taken to Room Level -1, which causes glitches. By continuing to use "Return" one can go even further into the negatives. The Warp spell takes the player to the last point at which the party were at Room Level 0. In terms of normal gameplay, this should always be the world map, but it is possible to get to Room Level 65 and then use a "Return" door, and as far as the game is concerned, Room Level 0 and 64 are one and the same.

Anything that's a negative Room Level will be using invalid data used for other things in the game, like the positions of vehicles, config options, or character stats.