Only Extreme 218 Straight Up

Barely escaping the bypass, Manuel Castillo’s Only Extreme 218 gets tough, and brings out some seldom used methods. 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.


Then 218 announced its intentions with irregular 457-wings.  First, consider the SE 57 wing winked to the NE hinge by a lumped 5-chain. Two regularly attached 47 wings pair with it to generate removals. In black, a lumped 5-chain hitches a ride on one link of the irregular 457 wink. One ANL victim requires 5-chain vision to see one of the toxic terminals. The SW 5’s provide a slink (orange) for the chain and a wink  (green)for the victim.

I don’t look for these things. They happen. We use slinks for chain winks all the time, but it’s rare to see two candidates slink and wink for different removals simultaneously.

When the smoke clears, there’s s a regular 671-wing in the South band.



It can also be interpreted as an ALS_XZ.



That was great, but lacking anything more  bv scan or panels, I start two clusters.  When blue/ green stalls, red/orange is extended from  a quad of slinks box in the South band.

AIC hinges are added next. These are segments that include a wink between cell candidates that partner in a slink with a candidate outside the cell. The hinges are construction blocks for AIC chains, similar to bv for XY chains. Note that aligned triple candidates do not form AIC hinges because they lack slink  partnerships by aligned triple

One hinge anchors an AIC nice loop, extending both clusters.

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

Not(red and green =>

Orange or blue.


either of the three-way AIC hinges form a slink between orange and blue, merging red with blue and orange with green.


The blue/green

traps => SE4

=> (E4, E7)

=> blue.

That wraps up Only Extreme 218.






Next week, , a reminder of what to do when you’re stuck, as I expected to be here. We’ll do a deferred trial introduced in Sysudoku, the Single Alternate Sue de Coq, on 218.

Its on the line marked grid. Can you find it and run the trial?






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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