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.

KDST 585 Favors the Bypass and Coloring


In spite of a big bypass, Krazydad Super-Tough v.5, b.8, #5 requires some work. An extensive XY railroad looks good, but a comparison with Medusa coloring favors the latter. This brings an opportunity to show unusual coloring resolutions, one involving … Continue reading

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KDST 575 Highlights Box Marking


Box marking gets to shine in the redo of Super-Tough, volume 5, book 7, #5. Here is the grid after the relatively modest bypass. The fill strings show where 4-fills were examined, but only one was found. In this snapshot, … Continue reading

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Super-Tough 565 Wrapped Twice


In this post, KrazyDad Super-Tough v.5, b.6, #5 survives a wrap of one coloring cluster, only to fall to a second. The bypass starts with two 3-fills, one resolved. Then in line marking, there’s an outbreak of naked pairs. Here … Continue reading

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KrazyDad Super-Tough 555


This post’s  basic trace on Super-Tough v. 5, b. 5, #5 illustrates the full use of 3-fills in the bypass, and closes with a six node remote pair. On the grid as the bypass is completed, S9 is marked as … Continue reading

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Krazydad Super-Tough 545 Wraps Up Fast


It’s mostly in Basic with Super-Tough v. 5, b.4, # 5. The post of March 26, 2013 reports a long XY chain, followed by two remarkable irregular XYZ-wings, then two finned swordfish. However, this update shows that the generous bv … Continue reading

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KDST 535 Trips on a Basic X-Wing


The X-wing is the easiest fish to spot. So easy, that the process of line marking finds it if you’re paying attention. KrazyDad’s Super-Tough v.5, b.3, #5 demonstrates. The last line marked was r1, because it had the most free … Continue reading

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KrazyDad Super-Tough 525 Review Update


This post has an updated solution of KDST 525, starting with a 3-fill and a rare remote pair. The bv scan has an irregular XYZ-wing, and the 6-panel features a  long XY nice loop that illustrates the XY Railroad on … Continue reading

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KrazyDad Super-Tougn 515 Starts a Review Update


This post begins the update review of the Super-Tough collection available on krazydad.com with volume 5, book 1, number 5. The Super tough collection was first reviewed in March 2013, but that was one of the first reviews on Sysudoku, … Continue reading

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Two Dave Green 4-fills


This post reports Sysudoku Basic on the two Dave Green puzzles of the previous post. In the Sunday 5-star of 4/17/21 on the left, a 5-fill becomes a 4-fill when N6 drops in. It is immediately  resolved to a 3-fill … Continue reading

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Complex 1-ways Take Out KDI 475


This post updates KrazyDad Insane v.4, b.7, #5 with a bypass 4-fill and a solution free of trials, unless you consider the complex 1-way a trial. To the line marking, we add Beeby’s UR. If 6r1c7, the 9 slinks carry … Continue reading

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