Invisible

Invisible
Internal ID	28
Character	#char 32 (0x20)
Category	terrain
Stats?	no
Other traits
Effect on movement	wall
Destructible?	no
Uses ZZT-OOP color names?	yes

The invisible element is one of the built-in wall materials in ZZT. It is a wall tile that, as indicated, initially appears invisible except for its background color. However, when the player touches it, the engine announces, "You are blocked by an invisible wall." and places a normal in its location.

The invisible has been frequently used to make invisible mazes and forcefields since the official worlds. However, most modern games use a ZZT-OOP program that performs an #if any check on normals of a particular color, and then uses #change on invisibles to execute a fade effect displaying normals, breakables and water before changing them back to invisibles. Besides being a more accurate depiction of forcefields, this allows the player to very briefly see the structure of the invisible maze, preventing frustration.

Invisibles can be placed by the engine, programmatically or not, in the seven default ZZT-OOP colors, and external editors allow them to be drawn in any available color. If the background is not black, the invisible initially appears as a solid block in the background color until it is touched, so such invisibles are best used around decorative fakes where both the foreground and background colors are the same.

In the internal editor, invisibles are rendered with #char 176 ░ (0xB0) for the benefit of the designer. External editors replicate this, though some applications make it optional.