Go way beyond difficult, with the hardest, most brain-busting sudoku you've ever seen! Calling all sudoku-solving diehards: with every puzzle requiring upper-level strategies, this collection packs even more of a punch than our previous Beyond Black Belt Sudoku. Get ready, because you'll encounter common advanced techniques with curious-sounding names like XYZ-Wing, Finned X-Wing, Sashimi X-Wing, Swordfish, Jellyfish, Gordonian Rectangle, and Gordonian Polygon. And you might find some tricky new things here, too, from Grouped X-Cycle and Simple Grid Coloring to 3D Medusa and Bi-Value Universal Grave. The sudoku generally become increasingly difficult as the book goes along, from "pretty darn hard" to "excruciating." Are you up for the challenge?