An ABJ Bronze With Many 4-Fill Bypass Traces


This post demonstrates the type of bypass you get by following up every resolvable 4-fill as it appears, in a less difficult puzzle. Bronze is the least difficult level announced by ABJ Creators. A similar solution path is started on any of four other 4-fills on the CREATORS Chrome of Sunday, April 3, 2022 givens grid, that immediately resolve.

On the 4-fill r1[2479], NW2 and NW4 see two free cells in r1, and E4 sees a third, placing NE4 in r1c7. Now on the trace, you can mark the 3-fill r1[279] left in r1, or be assured that the trace reader will note that SW7 sees a second 7 left in r1, placing NW7. That leaves two r1 cells for 2 and 9 and NW2 sees one of them, placing both values. The same effects list, in a different order, happens if you notice the 7 placement first.

That’s the way it goes.  It’s easier to check for a resolution of a 4-fill before entering it in the trace. Just check the clues in boxes with two free cells for missing values. Follow up on the missing value by checking for a third free cell seeing it.  A hit signals a resolution. It’s even easier with a 3-cell box. Just place the missing value in the outside cell.

Can you use the missing value rule to spot the other 4-fills that start the bypass with a resolution? You can compare your survey results with the full report at the end of this post.

In the final grid the pencil mark values were placed as effects, but were never used as causes, so they represent an over-supply of information for the solution.

This is how the other four 4-fills start the trace.

Next week, diligent spotting yields no  bypass 4-fills and there is not much of anything else, but box marking brings in the solution.

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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