An optical illusion has gone viral on TikTok after a woman asked people to stare at the black dot in the centre of a rainbow ...

Often optical illusions are made for fun ... She pounced right in and asked viewers to "stare at the black dot in the centre of the rainbow". She added: "Keep looking at it, count for 15 seconds." ...

Brainteasers are a delightful way to challenge your wits – and optical illusions can work wonders ... she invites viewers to ...