This optical puzzle tricks the eyes, activating visual awareness and focus.
Success depends on your ability to quickly spot tiny differences that may reveal the secret number.
Keep practising observation, and your eyes will grow better at solving complex visual problems.
The unique arrangement of numerals, notably 3996, hides a challenge for keen eyes.
Your eye acuity and attention to detail were impressive if you noticed this variation in 8 seconds.
Don't give up—optical illusions are tough and better with practice.
Look attentively at the picture to see the Hidden Number 3999 in the highlighted region.