New Delhi, July 13 -- Fun optical illusions have become the new pastime on the internet. They have led to friendly competitions between friends and left many individuals scratching their heads. Whether it's about finding hidden details in images or solving small puzzles, these challenges test how fast your brain can observe hidden details.

One such viral optical illusion requires you to find the number '993' hidden in a grid. But, it's not that simple because the grid is full of similar-looking 998's and you just have 15 seconds to spot it.

At first, you may think that it's a simple task to find the '993', but when you look carefully, the '998' are placed so close to each other that it will be difficult to spot a number with a single di...