India, July 17 -- Optical illusions mess with a person's head in the best way. What looks simple at first glance quickly becomes a brain teaser that one cannot look away from. This latest one is no exception. A grid filled with the word "cool" hides a single, sneaky "dool." If it looks easy, take the test and put a timer on; seven seconds is all that is allowed.

It is not only about eyesight, these kinds of mind-bending puzzles also test focus, speed, and provide a little bit of fun. So go ahead, give it a try. You might surprise yourself, or just wonder how to solve it.

The fascinating part about optical illusions is that it is a brain exercise, which also involves fun. What makes this illusion so challenging is how our brains only gra...