Sunday Recreation (Okidoku)

A piece on recreational grid math puzzles (the Sudoku/Ken-Ken variety):

http://www.edutopia.org/blog/recreational-educational-value-math-puzzles-deepak-kulkarni

...introduces the reader to a relatively new one called OkiDoku (similar, but perhaps more challenging than Ken-Ken).

Here are a few more websites on OkiDoku:

http://anglepointgraphics.org/?page_id=15
http://www.matholympiad.info/Pages/OkiDoku.aspx
http://www.okidoku.org