Category Archives: Puzzle Reviews

Reviews of preselected puzzles from published collections. Summary review table, and highlight analysis.

An ultrahardcore 91 SASdC Unlocks Beeby and Sudokuwiki


Here is the basics launch on Stefan Heine’s ultrahardcore 91, which quickly runs my two assisting solvers out of humanly practical removals. A Single Alternate Sue de Coq  trial reduces two clusters two one, and produces  two critical clues. In … Continue reading

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Ultrahardcore 47 Pattern Trial


This post bypasses Sudokuwiki’s  forcing chain parade with a value pattern trial, strengthened by the Single Alternate Sue de Coq analysis of the last post.  One pattern is tried and fails, leaving a coloring cluster. When the trial of the … Continue reading

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Ultrahardcore 47 Single Alternate SdC Trials


This post does the basics on the second Stefan Heine ultrahardcore right page under review.  Then it shows eight ways to do the five advanced moves up to forcing chains, two of them duplicated by boomerangs. It closes by  identifying … Continue reading

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Beeby on Heine’s ultrahardcore 3


This post highlights several moves from Phillip Beeby’s solver, which are alternatives to those appearing in the five earlier posts on Stefan Heine’s ultrahardcore 3. One result is a solution without the second blue green trial, left as a project … Continue reading

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Readers Solve Ultrahardcore 3


This post returns to the Stefan Heine’s utrahardcore  3 solution path just before cell and unit forcing chains. It turns out that an immediate coloring trial reaches a solution without them. Then we report how two Sysudoku readers solve it … Continue reading

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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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Ultrahardcore 3 Schlagt Forcing Chains


In this post, we continue with Sudokuwiki into forcing chain methods, and their relevance to the ultrahardcore theme. Sudokuwiki stalls, as Stefan predicts.  Then we fashion a trial for a logical, but practical outcome. On the grid after the red/orange … Continue reading

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Cell and Unit Forcing Begins in Ultrahardcore 3


This post reveals yet another way to start a boomerang, and reconsiders the practicality of Andrew Stuart’s Cell  and Unit Forcing Chains, this time facing an ultrahardcore right page. We get to a choice between Sudokuwiki and a coloring trial … Continue reading

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Utrahardcore 3 Lifts Off


The review of Sudoku ultrahardcore 1 right pages, a separate collection from (and tougher than) its left pages, begins with number 3, shown here post before last.  In this post, we follow Sudoku Basic and the Andrew Stuart’s Sudokuwiki solver … Continue reading

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A Bracket Busting Dave Green 4-Star


Here’s the  basic trace on the Saturday Dave Green 4-star shown at the end of last week’s post. It survived the three Sysudoku Basic  phases: bypass, box marking and line marking. It’s the first I remember. Let’s talk through the … Continue reading

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