Ключевые слова: adult, background, brain, brainteaser, challenge, challenging, closeup, crossword, difficult, difficulty, education, enjoyment, entertainment, exercise, fun, game, hand, hobby, home, indoors, intelligence, japanese, leisure, logic, logical, male, man, math, mathematics, mature, numbers, paper, pastime, patience, pen, pencil, person, play, playing, puzzle, senior, sheet, solution, solve, solving, sudoku, think, thinking, white, writing,