Go way beyond difficult, with the hardest, most brain-busting sudoku you've ever seen!

With every puzzle requiring upper-level strategies, this collection packs even more of a punch than Beyond Black Belt Sudoku. You'll encounter common advanced techniques with curious-sounding names like Sashimi X-Wing, Swordfish, and Gordonian Polygon, as well as some tricky new things, including Grouped X-Cycle and 3D Medusa. The puzzles grow increasingly difficult as the book goes along, from "pretty darn hard" to "excruciating."