Optical illusions are interesting images that can play with your perception and trick your mind. A good number of them are used as intelligence tests, and others are just only entertaining stuff to sharpen observation and focus. Intricate visuals give insight into how your brain would process the visual information.
source https://timesofindia.indiatimes.com/life-style/health-fitness/de-stress/optical-illusion-only-those-with-sharp-vision-can-find-an-insect-in-4-seconds/articleshow/117377301.cms
source https://timesofindia.indiatimes.com/life-style/health-fitness/de-stress/optical-illusion-only-those-with-sharp-vision-can-find-an-insect-in-4-seconds/articleshow/117377301.cms