The classic Sudoku is a numbre-puzzle. The rules are: every 3x3 square with a bold border contains eacht digit from 1 to 9 once, each vertical column and each horizontal row also contains each digit from 1 to 9 once.

Download here the Minibook Sudoku Collection as PDF File, it has the instruction and Puzzles from easy till extreme, a total of 8 minibooks!