Ключевые слова: abstract, background, black, blackwhite, board, cavity, checker, checkerboard, checkered, chequer, chequered, chess, chessboard, concave, contrast, convex, curve, deform, deformation, depression, dimple, distorted, distortion, gap, geometric, grid, hollow, hypnosis, indention, low, lower, meaningless, mesh, monochrome, monocrome, mosaic, opart, pattern, pepita, pit, recess, ripple, square, sunk, texture, tile, visual, void,