Oh! My Eyes ?

Our Eye
This picture is basically use to torture the criminals. This is only a part of it, because full image can cause poignant headache.
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The purple stripes are straight but it seems to be curved. Oh! My Eyes !
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There are no gray spots between these squares but you and me can easily see them. Why?
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Focus on the dot and move your head forward and backwards, you see that they are moving. How?
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