Invisible wall

An invisible wall is a boundary in a video game that limits where a player character can go in a certain area, but does not appear as a physical obstacle. The term can also refer to an obstacle that in reality could easily be bypassed, such as a mid-sized rock or short fence, which does not allow the character to jump over it within the context of the game. In 2D games, the edge of the screen itself can form an invisible wall, since a player character may be prevented from traveling off the edge of the screen.

In 3D games, invisible walls are used similarly to prevent a player leaving the gameplay area, however: visible boundaries such as stone walls or fences are generally preferred. 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. Nevertheless, designers might add invisible walls on cliffs to keep characters from falling off or use them as final borders of large open worlds, to make the world appear even larger than it actually is. Invisible walls often have an infinite height in order to make them unpassable.

Invisible walls can create discrepancies between a game's systemic logic and its fictional logic, as a game's rules dictate that one cannot continue past the wall, while the fictional setting cannot explain why this is. This breaks the supposed internal reality of the game. Because of this, invisible walls are harshly criticized for breaking player immersion, but such barriers may be necessary to "preserve the entertainment value of the game by keeping the game scenic ... improving overall immersion."

More novel ways of obstructing a player character from leaving an area, such as placing invincible enemies between the player character and the invisible walls, are considered an optimal tactic to keep the game scenic. This way, a player may feel reward for their attempts and find that the game's designer has considered the player's behavior.

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Wikipedia