Surprisingly good game! Nice job both of you. 6x6 took me a few minutes, after initially seeming impossible. I like much more than Sudoku cause it uses maths as well as logic. 9x9... not so easy :-)

Possible bug: I got some of the row/column numbers (outside the puzzle) turning bold black before I'd finished ruling numbers in that row/column in or out, not sure why. That was with the 9x9 grid.