Ключевые слова: 21, 3d, alphabet, alphabetical, char, character, concept, counting, design, digit, digital, education, element, equipment, figure, font, graphic, icon, illustration, isolated, learn, learning, letter, mathematic, mathematical, number, numeracy, numeral, numeric, object, one, order, preschool, school, single, solid, study, symbol, teaching, text, training, twenty, type, typography, white background, wood, wooden,