
You can find this nice sudoku variation on http://www.thegriddle.net
There are also other sudoku variations like shape sudoku, multi sudoku,
stretch sum sudoku, funky kakuro, quad clue sodoku, ....
sudoku - kakuro - hitori - hashi - slitherlink - battleship - pic-a-pix - link-a-pix - fill-a-pix - maze-a-pix - dot-a-pix - tents - centriko - hexa-trex - squaro - futoshiki - trigon - trizm - kenken - kendoku .................