All examples are black and white images, partitioned by lines such that crossing a line switches the background color and the foreground color. (Sometimes it is not clear which is "background" and which is "foreground".) In the space between two dividing lines, there is a black and white scene; the outlines of the shapes are curves dividing black from white. Images sorted left are such that each outline-curve present in a scene that comes in contact non-tangentially with a dividing line continues across the dividing line, across which the black and white sides of it switch.

Examples (especially right) usually have ambiguity to some degree; depending on how a person reads the images, dividing lines may be confused for curves within a scene.

All examples are black and white images, partitioned by lines such that crossing a line switches the background color and the foreground color. (Sometimes it is not clear which is "background" and which is "foreground".) In the space between two dividing lines, there is a black and white scene; the outlines of the shapes are curves dividing black from white. Images sorted left are such that each outline-curve present in a scene that comes in contact non-tangentially with a dividing line continues across the dividing line, across which the black and white sides of it switch.

All examples (especially right) have ambiguity to some degree; depending on how a person reads the images, dividing lines may be confused for curves within a scene.

All examples are black and white images, partitioned by lines such that crossing a line switches the background color and the foreground color. Left examples are such that each curve present in the drawing coming in contact non-tangentially with a dividing line continues across the dividing line.

All examples (especially right) have ambiguity to some degree; depending on parsing, dividing lines may be confused for borders of shapes in one "universe."

Same objects are shown lined up in both "universes" vs. the two "universes" are not aligned.

All examples are black and white images, partitioned by lines such that crossing a line switches the background color and the foreground color. Left examples are such that each curve present in the drawing coming in contact non-tangentially with a dividing line continues across the dividing line.

Aaron David Fairbanks