Tag Archives: irregular XYZ-wing

Ultrahardcore 3 Falls to Coloring Trials


This post reports coloring trials that gain the solution after forcing chains when Sudokuwiki gives up.   This includes an example of a grid diagram illustrating the route to contradiction in a breath first trial trace. Then we close with a comment  … Continue reading

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The Especially Nice Loop of KD Insane 465


This post reports several features of an update of the post that introduced nice loop coloring. The illustrating nice loop was in itself remarkable. As shown already from books 1 through 5, KrazyDad’s hardest, the Insane collection, is hard enough … Continue reading

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Funster Extreme 46 Not So Much


The review of Charles Timmerman’s funster Hard to Extreme Sudoku continues with Extreme 46. It’s  entertainingly advanced. Extreme 46 has its moments.  The basic trace is spread across the page with 3-fill after 3-fill. Two unusual events occur in box … Continue reading

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Coloring Dominates Very Hard III-15


The review of Moito’s Road to Mastery Sudoku continues with another example of early coloring and its cooperative interactions with the X-panel. The advanced path is similar to that of Very Hard I-35 two posts back, but this time coloring … Continue reading

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How Not to Find a Multiple on Moito’s Road


After a jaw dropping irregular XYZ-wing, a marking mistake reveals an unavoidable UR and two solutions of Very Hard IV-6, then the correction leads to an even more remarkable, but no less unavoidable uniqueness violation. Coloring reveals the logical path … Continue reading

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Only Extreme 218 Straight Up


Barely escaping the bypass, Manuel Castillo’s Only Extreme 218 gets tough, and brings out some seldom used methods. An alternative trial path by Single Alternative Sue de Coq, normally held in reserve,  follows in a second post. The bypass filled … Continue reading

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The Akron 2017 Championship Sudoku


This is another Sysudoku analysis of the championship puzzle of the Sudoku tournament put on by the Akron-Summit Public Library. It’s an annual tournament of four rounds, the last being a three person solve – off on poster board grids, … Continue reading

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Cluster Extension by Not-Both Trials


In this post and the next, the first puzzle of the Manuel Castillo Only Extreme Sudoku review, Only Extreme 3,  is taken ahead of the review of his Only Hard Sudoku. The reason is in the title. Rounding out the … Continue reading

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The Limited XYZ-wings of THLS


The XYZ-wing is limited in The Hidden Logic of Sudoku, as it generally is in Sudoku literature, by  a limited conception of the weak link.  This post presents a resolution of Royle 17-12407 using an iXYZ-wing, a form of the … Continue reading

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The KrazyDad Insane Review Begins


This post begins the Sysudoku review of Jim Bumgardner’s toughest collection, the Insane level,  with a demonstration of cluster extension in Medusa coloring, via Limited Pattern Overlay.  The post was updated in 10/18. The first review puzzle is Insane v.4, … Continue reading

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