Stare at the center of the flag for several seconds. Try not to blink! When you are ready hold down the space key. What did you see? Press the 2 key to toggle to a different illusion. Stare at the star at the center of the image for several seconds. When ready hold the space key down. What did you see? Press the 1 key to toggle back to the flag
Examples of Retinal fatigue. Flag illusion from Norm Herr (adapted from a CSCS activity) The castle illusion seen online and on Nat.Geo. Brain Games (television show).
