Ключевые слова: abstract, app, background, blank, book, button, concept, cover, description, design, diary, document, education, email, empty, flat, goods, graphic, icon, internet, isolated, knowledge, laptop, learning, library, lines, literature, marketing, media, mobile, old, open, page, paper, reading, retro, set, shadow, shape, shopping, sign, simple, stack, style, tablet, teaching, text, textbook, web,