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. Additionally to this rules, this Sudoku includes < and > :
Smaller < Bigger
Bigger > Smaller

Download the PDF Dokument here, with Instructions (in German) and Riddles from Simple till Extreme.