A sudoku puzzle is solved by placing the digits 1..9 in each of the cells such that no value is repeated in any row, column or in any of the nine marked 3x3 blocks.

A killer sudoku has groups of cells formed into cages ( bounded by broken lines ). There can be no repetition of any value within a cage. Furthermore, the values placed within the cells in the cage must add up to the stated sum ( if given ).

There can be no repetition of values along either of the main diagonals in a '-X' sudoku puzzle. A windoku puzzle has four extra 3x3 blocks. With equality/inequality killer sudoku puzzles, cage sums must obey any stated '<', '>', '=' relations.

Every puzzle has a unique solution which can be derived logically and without guessing. There are six new puzzles every day: three killer sudoku of varying degrees of difficulty, one zero killer sudoku, one inequality killer sudoku and one inequality killer windoku-X. Previously published puzzles can be found in the appropriate archive.

The puzzles are presented as 6-12kb PDF documents which can be easily printed or saved to disc and are updated daily at 0100 GMT.

Individual puzzles may be reproduced without permission for non-commercial purposes.

There is an email address for reporting broken links, missing puzzles or any other goofs/gaffes which will appear now and then. Comments and suggestions are always welcome.