Magick Eye
I bet you all remember these but for the ones who forgot:
The images can be easier to see if viewed on paper rather than a computer screen. So you can print out the image but it's not necessary. (You don't need to print in color.)
Hold the printed image RIGHT UP TO YOUR NOSE and STARE through it as if looking off into the distance. The image will be blurry, try not to blink. Move the page VERY SLOWLY away from your face until the two circles above the image turn into three. If you see four circles continue to move the image away from your face until you see only three circles. At this point hold the image still until the 3D illusion slowly comes into focus and the hidden object magically appears! The longer you look, the deeper and clearer the hidden image will become.
Have fun 😄