Bookraft

The New York Times is introducing a math and logic game called Ken Ken derived from Sudoku. Its origins are again from Japan. The basics of Ken Ken is that just like Sudioku: the the number from 1-4 ( or 1-n depending on the puzzle size) have to be laid out in all the puzzles columns and rows such that:
a)each column has one each of the numbers (for a 4 square ken Ken that is 1,2,3, and 4) and so too each row;
b)no number may be repeated twice in any row or column.
This is the classic Sudoku rules. What Ken Ken adds are mathematical constraints (linear programmers and math optimizers will be familiar with this notion).

The constraints are indicated by a thick border around the number cells and the numeric value these cells number must equal. For example in the puzzle above the top left hand corner constraint says the two numbers when multplied together must equal 6. Each constraint is indicated by a thick border around the cells involved. This is the attraction of Ken Ken over Sudoku - the solution is not "seeded" with numbers; and the logic of the game involves solving the math constraints. Returning to our example, the only way one can get to 6 by multiplication of any two of the numbers 1,2,3,4 is 2*3 or 3*2 - so this tells what numbers have to go into the cells but not the order. This is the fascination of Ken Ken: math restricts the possible numbers, then Sudoku logic determines which numbers go where. Pretty quickly the 4 sided game becomes trivial and adventure in 6-sided or greater become more satisfying.

Try this Google Gadget version for yourself: