The Lucy - visible element represents the flag of Lucy's visibility. If Lucy is visible, her motion over the sheet is animated according to the definition of the Lucy sprite's definition. Lucy's visibility being switched off, Lucy's motions over the sheet are executed immediately.

 

The element of Lucy's visibility can be treated as a normal logic variable. By using it in a logic term it can be tested, if Lucy is visible. Under "visibility" is understood the possibility of doing animations of the Lucy sprite independently on whether Lucy is present in the sheet visible portion. By using the visibility element as a command its value may be set by means of a logic term, thus switching Lucy's visibility on or off. In case a preceding command to step or to shift to a specified coordinate has been given she will first finish the shift before the visibility can be switched on or off.