Are you ready to engage in a fun-filled optical illusion? Welcome to this ultimate challenge of optical illusion to test your IQ. This viral puzzle is designed to test your brain power, attention to detail and quick thinking to the limit.However, not everybody can solve this in one go, because the challenge is to spot the hidden number in 6 seconds.The challenge is simple in concept but tricky in execution: within just 6 seconds, can you spot the inverted number 39 hidden among a sea of inverted 63s?At first glance, the sequence of numbers may seem ordinary, but the trick lies in the optical illusion created by flipping the numbers upside down. When the numbers are inverted 3 and 6, they start to look alike, while 9 and 6 also look remarkably similar to each other. This makes it surprisingly difficult for the brain to immediately distinguish between 39 and 63. The mind must process the subtle differences in shape, orientation and placement, all under restricted time.How to approach this optical illusion:This type of puzzle is more than just a fun activity. It tests several cognitive skills at once. You need sharp observation to notice minute differences, quick pattern recognition to separate the unique number from its lookalikes, and mental agility to make a fast decision. Adding the 8-second limit pushes your brain to operate under pressure, similar to real-life situations that require rapid thinking and problem-solving.For those curious about the solution, careful observation reveals that the inverted 39 is positioned a few rows up from the bottom on the right side of the sequence, often highlighted with a red circle in demonstrations. The challenge may seem simple once you know the answer, but finding it in real time requires focus, sharp eyesight, and a keen eye for detail.Whether you enjoy brain teasers, want to sharpen your observation skills, or just like testing your IQ in a fun way, optical illusion puzzles like this provide a stimulating mental workout. They engage the brain in ways traditional puzzles do not, combining speed, perception, and cognitive reasoning.Just grab a timer and get on with it and remember take no help! Focus on the numbers and see if you can spot the inverted 39 in under 8 seconds. It is a small task with a surprising mental payoff, proving that even a few seconds of sharp attention can reveal alot.