A player might get stuck in map geometry with no way to escape or to die. A player might be able to find a specific spot where they do not have to move to gain experience, because monsters are constantly spawned but can be easily and immediately killed. In multiplayer maps, a player may be able to reach areas of the map designed to be inaccessible, for example, reaching an advantageous rooftop position and camping other players. In the worst case, a player might be able to fall out-of-bounds of a map where other players cannot reach them. Invisible walls are cited to be level design bugs, and might be "left-over geometry" from an earlier version of the level or an object's improperly aligned "collision box".