Author Archives: Sudent

About Sudent

I'm John Welch, a retired engineering professor, father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. Sudoku analysis and illustration is a great hobby and a healthy mental challenge.

A Lite Coloring Update of Castillo’s Only Extreme 261


This post is the first of several which update earlier review solutions to include a new guy in town, lite coloring. The earlier posts will be left as they are, except for added links to these updating posts. Instead of … Continue reading

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An Error Hides a Lite Coloring Trap on ultrahardcore 399


This post corrects an error on the post of December 8, that prevents a lite coloring trap in ultrahardcore 399. Then there’s follow up on the trap, with the lite coloring marking in place. Trial is not avoided, but the … Continue reading

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Lite Coloring in a Red Russel Special


This post explains lite coloring as I understand it from comments and emails from its apparent inventor, Dov Mittelman. I only know Dov as a reader of this blog. He (or she) does his analysis in his head and on … Continue reading

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Pattern Trials Peel the UHC 487 Onion


The ultrahardcore review ends, with Stefan Heine’s 487 giving up a naked single and two skyscrapers, and a jaw dropping complex 1-way, shuts down the solver team. Slicing at it with three onion peeling pattern trials leaves very little for … Continue reading

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SASdC Unlock UHC 443 for Beeby


After the hidden unique rectangle hinted last week, a pair of Single Alternate Sue de Coq trials gets the review solver Beeby moving again. ALS-wings and a finned X-wing get us to a colorful finish. The hidden unique rectangle left … Continue reading

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Beeby Softens Up ultrahardcore 443


This post reports a series of Beeby ALS-XZ featuring alignments in Z and X, almost to the point where a trial is needed. A simple basic trace means a hard start, with a crowded grid. Sudokuwiki’s 579-wing is a Beeby … Continue reading

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Lite Coloring Informs a UHC 399 Trial


In one post, the 10th ultrahardcore review puzzle is wrapped, but not without an introduction of something new in Systematic Sudoku. Ordinarily advanced steps begin in line marking, and lite coloring is introduced. In line marking Stefan Heine’s ultrahardcore 399, … Continue reading

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An SASdC Trial Defeats ultrahardcore 355


In this post a SASdC trial plays like a regular hard puzzle from other collections. The trial amounts to adding two clues, and seeing  what happens.  But it isn’t guessing, and instead of making a small gain, the trial solves … Continue reading

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UHC 355 Provokes a SASdC Trial


After a typical ultrahard Sysudoku Basic, Sudokuwiki starts with an APE so unusual as to change my working definition of the APE. APE stands for Aligned Pair Elimination.  From every example so far, I thought it was the two elimination … Continue reading

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A Coloring Trial Weakens ultrahardcore 311


Sorry about last week’s post arriving a week earlly. This week continues the solving of Stefan Heine’s ultrahardcore 311 with a coloring trial, and an enabled Beeby marching to the solution. Here is the trial grid, after the removal of … Continue reading

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