Created in the United States, these addictive conundrums were originally called "Number Place" puzzles until their recent rise in popularity in Japan, where the name translated as sudoku. However, in a true sudoku, unlike a "Number Place" puzzle, the grids are symmetrical. This trait makes for a more elegant solve. Every puzzle included inside is symmetrical, which is not always the case in other sudoku books.

In this "Martial Arts Sudoku" series, we've indicated the skill level necessary to complete each book in the same way Japanese karate levels are ranked: by different colored belts. This is the Second-Degree Black Belt volume, filled with puzzles that will provide a sly, absorbing test for even the best, most proficient experts.

You'll go crazy for these super engaging brain bafflers!