Japanese Ken

Times, i.e., Will Shortz, started daily dose of a new puzzle called KenKen (loosely, cleverness, cleverness). It is basically a Sudoku-like square of permuted digits but each bold subsquare comes with an arithmetic operation (+,-,*,/) and a purported total that numbers within that bold subsquare should yield when the operation is performed. These operations, when not commutative (-,/) can be applied in any order to the numbers in the subsquare. Rest of it is as boring as Sudoku. May be people will study the complexity of this game too.