There are many excellent puzzle sites freely available, have you seen the excellent Set Game from the New York Times? How many sets can you find? Click ‘How to play’ in the menu on the left for the rules. A new puzzle is set every day.
Other favourite puzzle sites are provided here on Mathematics – Games. Erich Friedman’s Puzzle Palace site for example includes numerous mathematics puzzles.
Another great collection comes from Simon Tatham, I have been enjoying his ‘Untangle’ puzzles; note that it is possible to change the number of nodes – use the Type menu.
You may be familiar with Suduko and Kenken type puzzles, have you seen Rogo?
Wishing students everywhere a very Happy Christmas. Good luck with any examinations you may have early in 2013.