Ключевые слова: abstract, art, background, ball, bluff, center, circularly, concentric, concept, crescent, deceptive, delusion, distorted, endless, eyesight, fallacy, fancy, fantasy, hole, illusion, illustration, imagination, middle, motion, motley, mottled, movement, moving, optical, pipe, purple, rotating, round, shapes, space, spheres, surface, surreal, trick, vision, visual, visually, yellow,