1.0 link Rainbow Dash Network http://rainbowdash.net/ Narwhal (narwhal) http://rainbowdash.net/narwhal http://rainbowdash.net/notice/3863578 This is a popular example of the phenomenon, you've probably seen it before. Tile A and Tile B are both actually the same colour, but because out brain assumes shadows make things darker we assume that Tile B is lighter than it actually is. <a href="http://upload.wikimedia.org/wikipedia/commons/6/60/Grey_square_optical_illusion.PNG" title="http://upload.wikimedia.org/wikipedia/commons/6/60/Grey_square_optical_illusion.PNG" class="attachment" id="attachment-819198" rel="nofollow external">http://upload.wikimedia.org/wikipedia/commons/6/60/Grey_square_optical_illusion.PNG</a>