The name "Sudoku" is the Japanese abbreviation of a longer phrase, "suji wa dokushin ni kagiru" (数字は独身に限る, "suji wa dokushin ni kagiru"?), meaning "the digits must occur only once".

The numerals in Sudoku puzzles are used for convenience; arithmetic relationships between numerals are irrelevant. The attraction of the puzzle is that the rules are simple, yet the line of reasoning required to solve the puzzle may be complex. The level of difficulty can be selected to suit the audience. Bear Today Shop offer a free Sudoku puzzle in three levels of difficulty, each time you start a new game you will get a new puzzle.