A checkerboard... that moves?

This recreation of an optical illusion was made using Maple Learn. For an interactive version where you can zoom into the plot and change the colors, check it out here: Optical Illusion: Moving Image. The buttons in the document were made possible by deploying the canvas from Maple using this Maple script.

Changing the colors creates cool visuals - and the motion of the image is apparent using some color schemes more than others.

How Does It Work?

If you zoom really far into the image, you can see that it is made up of a checkerboard in the background, with crosses (plus signs) covering each of the corners:

The checkerboard is made up of unit squares, and to create a cross with hieght=6d, centered at (x,y), polygons were used:

Polygon(
  [x+d,y+3d], [x+d,y+d], [x+3d,y+d],
  [x+3d,y-d], [x+d,y-d], [x+d,y-3d],
  [x-d,y-3d], [x-d,y-d], [x-3d,y-d],
  [x-3d,y+d], [x-d,y+d], [x-d,y+3d]
)

The key to the motion of the image lies in the alternating 1-1-2-1-1-2 pattern of the light/dark crosses along the diagonals.