Extra tricky.
But kee.
In each of these more than 300 handcrafted puzzles, ranked by difficulty from expert to x-treme to ultimate, every move is an adventure, a one-on-one challenge with a grandmaster who delights in elegance, symmetry, and building in the occasional roadblock.
If you\'re craving the challenge, sharpen your pencil and pit your wits against the Japanese puzzle-makers at the top of their game.
It\'s the sudoku collection that\'s not for the faint of heart.
Extra tough.
Extra tricky