Optical illusions

We had lots of fun playing with various optical illusions and spectral effects in class this morning. This one requires you to focus on the cross in between the four rectangles for about 15 seconds - then quickly look to the blank space on the right and DON’T blink! You will see (although it may not work on screen!), briefly, the opposite colour in the place of the one you’ve been looking at. Give it a go! (A bigger screen is better.)