Only Extreme 218 Straight Up


Barely escaping the bypass, Manuel Castillo’s Only Extreme 218 gets tough, and brings out some seldom used methods. This revisit of October 2022 is aided by PhilsFolly solver Beeby. An alternative trial path by Single Alternative Sue de Coq, normally held in reserve,  follows in a second post.The bypass filled in the center band and tower, leaving very little action for box or line marking stages.

The bypass filled in the center band and tower, leaving very little action for box or line marking stages.

On the XYZ-wing map are two i457-wings sharing the hinge cell and the grouped remote i57 cell.

These things happen when a forcing chain starts where you need a wink.

On the 5-panel, an ANL allows a regular 671 wing,

or an ALS_61.

Two small clusters are marked, then AIC building starts with a rectangular nice loop.

The 7r8c7 trap enables a skyscraper, but more decisively, a bridge:

Not(red and green => orange or blue.

But now, a light coloring wrap:

green  => green 3r3c5  =>green 2r7c3  =>

green is false

In the red/orange expansion,  after the 7 r9c8 trap and the SEr9 boxline,

The naked pair in r8 forces a second orange 7 in r9, wrapping orange.

The colorful solution.

Next week, a reminder of what you do when you’re stuck. We’ll do a deferred trial introduced in Sysudoku, the  Single Alternate SdC on Only Extreme  218. It’s on the line marked grid.

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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