Way Beyond Black Belt Sudoku : Martial Arts Sudoku Super-duper Tough, Paperback by Longo, Frank, ISBN 1454933577, ISBN-13 9781454933571, Brand New, Free shipping in the US 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 th goes along, from “pretty darn hard” to “excruciating.”
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