I read about KenKen® (also known as CalcuDoku) in the New York Times the other day, and decided to write a program that creates similar puzzles. The rules are: (1) the 4×4 puzzle uses the numbers 1-4, the 6×6 the numbers 1-6, and so on. (2) in each row and in each column each digit can appear only once (just like in Sudoku). (3) each "cage" (the blocks with the thick border) shows a result and an operation (addition: +, subtraction: -, multiplication: ×, or division: ÷). The operation applied to the numbers in the cage should produce the result shown. Note that for subtraction and division the order is not fixed (!) Look at the solutions of earlier days to make things clearer.
You can solve the puzzle on the page using the arrow and number keys. Use the spacebar to clear a cell. Use backspace to undo a move. In the 10x10 Calcudoku puzzle (every Sunday), use the zero key to enter a 10.
Recently (January 25th) two books with 100 of my puzzles each were published by Alpha Test, a well-known Italian publisher of puzzle and test books. The puzzles are called 'Newdoku' in Italy. Here's a page describing the first book, one for the second book, and here's a page where you can order them both at a 20% discount. The pages are in Italian though. The people at Alpha Test do speak English, if you want the books you could try the 'Richiedi Info' (request information) link at the right of the page. Ideally they'll find publishers/distributors for other countries.
