Some might ask you to spot a certain thing, while others might speak about your personality. An optical illusion is like a magic trick for our eyes, making us see things that aren’t really there ...

Optical illusion: Find the hidden number in this mind-boggling challenge. ... While the image may just seem to be a patch of purple wallpaper, ... Some of these challenges can be very tough to solve.

Some Twitter users went beyond five minutes trying to work out the illusion. "This brick wall illusion made me go loco after staring at it for about half an hour," user Andy said. Others just ...