Next, let's play with some words.
What do you see?
In black you can read the word GOOD, in white the word EVIL (inside each black letter is a white letter). It's all very physiological too, because it visualize the concept that good can't exist without evil (or the absence of good is evil ).
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Now, what do you see?
You may not see it at first, but the white spaces read the word optical, the blue landscape reads the word illusion. Look again! Can you see why this painting is called an optical illusion?