Look carefully at the cube. Where is the blue side? Is it on the inner back or the outer front of the left side? The more you stare at the image, the more it will alter and switch from back to front. The perspective changes and suddenly the blue side is projected towards us, at the front, with the yellow receding.
The brain simply cannot decide where the blue side of the cube is. This type of cube is called a ‘Necker Cube’ and is a simple, but effective, optical illusion that keeps working, the more you stare at it.
Is the blue side on the inner left back or the outer left front?
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