Ключевые слова: abstract, add, addition, background, box, button, calculate, check, concept, correct, cross, design, divide, division, element, equal, equalizer, equals, flat, frame, frequency, geometric, graphic, interface, line, mark, measure, media, modern, multiply, music, number, object, option, pattern, plastic, plus, positive, realistic, set, shape, sign, signs, simple, style, subtraction, support, symbol, trendy, vintage,