Box Marking Subsets Maintain a CREATORS Collapse

Sysudoku weekly posts will soon be ending. This post may be the last one from the Akron Beacon Journal CREATORS series. In this one, Sysudoku box marking rescues us from a very stingy bypass, in ABJ Creators of 4/20/22.

The bypass trace, shows no 4-fills or 3-fills.  The two 4-fills created by the bypass, c2[1234] and c5[2578], are not marked on the trace or the grid because they don’t resolve immediately. The spotting check: in c2, values 578 that see two fill cells are not missing. In c5, 3 and 6 are not missing, and 8 does not see a third fill cell. Value 5 sees three fill cells in 5-fills r6 and r7, one short.

Box marking is almost complete, when the 8 slink joins the 2-slink in the North box for a naked pair N28 to start a collapse.

The collapse carries to the solution,

when NW3 creates the second naked pair NE36.

Weekly posts continue with three Basic level puzzles from Hard Sudoku for Adults, by Kampbelmann , dated without copyright notice April 2020, among the toughest I tried on paper without tracing and full 3 and 4 fill analysis.

Next is Kampbelmann 50, which can be solved in Sysudoku Basic bypass.

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.
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