Checker Shadow Illusion Solution
The squares marked A and B are exactly the same shade of
gray. If you don't believe the answer, you can copy the image
into a paint program and check the colors.
Or print the image out and cut out the squares and place
them along side each other. You will see they are
identical in color. Note that some printers have
"enhancement" processing that increases the contrast of edges.
This can cause the printed squares to have slightly different
values of gray.