Saw it. Liked it. Enough to post it.
(I recommend downloading before showing in class so as to avoid pop-up ad distraction. You definitely want to go full-screen.)
Having posted it, I now run the risk of being deluged with the comment, "I've seen that one a million times." If that statement captures your sentiment, felicitations! And you've been spared from the chore of commenting.
Due to some flaw in my character, I hadn't seen it before and was so struck that I was compelled to share. I tried recreating it with a photo of my own and it worked, but not as well.
I'm conversant in chromatic retinal fatigue, but there's a wee bit more going on here.
The classic chromatic retinal fatigue illusion is to stare at a color negative of a US flag, for example, then at a white surface. You see a ghostly Old Glory in its standard glory.
But look at the color negative here. Seems to be just orange and blue. The orange becomes the blue sky. But the blue? Curious.
Follow this link to see some illusions you've seen a billion times!