India, Aug. 7 -- If you enjoy brain teasers and tricky visuals, then this optical illusion might be your next obsession. It is simple at first glance, a grid full of the number 18 repeated over and over. But somewhere sneaky in there, the number 81 is hiding, and it is throwing people off everywhere online.

The challenge? Try to find 81 before your friends do. Some players claim they spotted it instantly. Others have been squinting at the screen for minutes. The illusion is playing with our brains using repeated patterns, a classic technique that confuses the eyes and makes it tough to pick up the difference.

It is not just about vision. It is about pattern recognition and the ability to catch small differences. The "1" and "8" are flip...