Real tough Sudoku

Sudoku became
world famous in the last months, although it exists since 18th
century when swiss mathematician Leonhard
Euler
discovered a puzzle game called Latin Square.
3doku
The name Sudoku comes from the japanese sentence:
数字は独身に限る
,
meaning as much as: limit to unique numbers.
Although published in various newspapers over the years, it reached
world wide fame quite recently.

Meanwhile there are also a lot of more complex sudokus for “the
advanced puzzle fan”.

Sudoku
with 16 sqaures and numbers.
sudoku4
Sudoku
as jigsaw puzzle, non square based:
sudoku-puzzle
And for the real freaks, pre-requistiting a computer, and probably
a 3D graphics card:
The ultimate 3-dimensional Sudoku called:
3doku, available for Mac and PC.
3doku
If you’re interested in the different mathematical approaches to
solve a sudoku take a look at wikipedia.