Fick’s Advanced Path on Only Extreme 3

In the pre-review post of August 29, Cluster Extension by Not-Both Trials, a series of coloring cluster expansions were made by testing the not-both condition for AIC slink coloring. Like other trials, this tactic is considered extreme here in Sysudoku. My friend Gordon Fick responded with a grouped AIC ANL which keeps Only Extreme 3 in advanced Sysudoku territory.  Here we use it, after the irregular XYZ, AIC nice loop, finned X-wing, and Sue de Coq of the pre-review post.

Here is the grid  after the follow up of the Sue de Coq, showing  the two AIC slinks  under consideration for blue/green expansion. 

Beginning in the NE, the AIC does a grouped 8-chain slink and reversed XY to 6-chain to XY terminal, removing two 8’s.


The follow up





brings the 6-wing that Gordon anticipated in his alert.






a new red/orange coloring traps 3r7c4 to wrap red and hand in the orange and blue solution.

Unless you consider Gordon’s AIC ANL extreme, and many would agree with that, Only Extreme 3 is only advanced.

Now to Only Extreme 46.

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A Surprising Dave Green Sunday 5-Star

My Sunday morning ritual Sudoku, the Dave Green 5-star of September 3, 2017,  sent me upstairs for PowerPoint support. This one breaks tradition by surviving Sysudoku basic, and with a heavy line marking. After no other advanced progress,  a four cluster coloring proves 10 solutions.  You get another demonstration of coloring as a humanly practical way to deal with multiple solutions.

The difficult line marking, and just getting through basic, were signs that this was not my typical Sunday treat.

Fortunately, I got it transcribed to the template before the newsprint version became unreadable. 

Nothing worked for me until this very indecisive coloring trap and possible bridge prompted more clusters.

The red vs. green conflict in r7 means blue or orange or both are true. But no 8’s see blue or orange.




I added pink/tan  and aqua/yellow clusters. No further conflicts, so I start a red trial. In the trial, yellow would generate a two- solution rectangle.

Discarding yellow, evidence of multiple solution appears as aqua and tan generate a four line extended rectangle in the East tower, while aqua and pink bring a third solution.

The multiple solution justifies going back to yellow in the red trial to pick up the rectangle multiple.  Blue, red, and tan accompany yellow, and an independent extended rectangle emerges, for four more solutions.


Finally, aqua/orange/blue trials add two solutions,  and aqua/orange/green provide the newspaper’s, the double sized .

Ouch! The unintended multiple solutions explain the sudden jump in difficulty from basic to extreme . The basic level record remains intact. Although BJ readers may question that with the 9/24/17 5-star I sat down to yesterday. It seems to require a one-term Sue de Coq, but one that could have been spotted in line marking. Dave, run the solver to the end. I don’t expect any more naughty 5-stars like this one, disturbing the Sunday morning peace.

Next week, I’ll post the less extreme ending of Manuel Castillo’s Only Extreme 3 that Gordon Fick sent me, and we’ll get on with the Only Extreme review.




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Bookends of the Only Hard

This post checkpoints the only sysudokie bypass casualty and the only sysudokie basic survivor, in this second review of Manuel Castillo’s Only Hard Sudoku collection. The report of my first review was posted 1 ½ years ago, March 29, 2016. That review used every 40th puzzle, instead of every 42nd, and had almost identical overall results. I was using the bypass then, but not the 3-fill. The overall results of the two reviews are consistent, with the 3-fill tending increase the length of effect lists in the basic trace.

Looking back, I can see an abundance of 3-fills in the bypass trace of Only Hard 254.

If that doesn’t describe your version, and you’d like a close look at the 3-fill, load up a grid and read the trace, noting the reason for each move.

Here’s the line marked grid for Only Hard 338.






And the basic trace:

Now prevention of each of the two available rectangles requires promotion of an extra candidate, and the removal of its slink partner. The removals are decisive.

The conclusion of both reviews is that the Only Hard collection is primarily basic level, with a wide range of collapse points.  The Castillo Only Extreme’s wait in ambush.

 Next post was intended to be Manuel’s Only Extreme 46, the second Sudoku of our Only Extreme review, but two more timely subjects have intervened.

First, the Dave Green Sunday 5-star of September 3, 2017 at right made a PR jump into advanced territory, and then was caught with multiple solutions. That’s next week. This is your chance to uncover multiple solutions yourself without a computer solver.  See the Multiples section of the updated Titles page (menu bar) for a list of post examples, by coloring trials.



Secondly, frequent contributor Gordon Fick sent me a better response to the imbalance of Only Extreme 3 which makes the cluster expanding not-both trials avoidable, and snatches back 3’s EXTREME badge as we start the review.

I’ll be posting my effort on Only Extreme 46 at left, on October 10.



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A Well Hidden Pair in Only Hard 128

This begins a brief review of Manuel Castillo’s Only Hard Sudoku, preliminary to reviewing his more recent Only Extreme Sudoku. Both books are wordless collections of 400 puzzles, with identical formats.

Thanks go to officers, members and guests of the Fairlawn Ohio Seniors Club, for a warm welcome. We walked through the start of  basic Sysudoku on a newspaper 4-star, and learned bypass slink marking, 3-fill rules, and importantly, how to read a Sysudoku basic trace. The audience started a handout grid, and have a full basic trace to finish the puzzle.

Now to Castillo’s Only Hard collection,  here’s a Sysudoku review table with preselection of 2, 44, 86, . . . , 380. The Only Hard range in Sysudoku survival from bypass to line marking close, with one brief glimpse at the advanced level.

Details of review table notations are on the Reviews page.

We trace Number 128 to show an untypical hidden pair.  I spotted it in my systematically plodding way, in the line marking close, but reading back in the trace, I realized it could have been spotted in box marking. Starting the 8: list, and adding 8 marks to the r9 naked triple, the 3 and 8 clues in the East box limit placement of the 38 partners to r2c8.

The usual hidden pair spotting aid, the naked triple, has not arrived. Here we depend on the definition of a hidden subset: n numbers in only n cells.

If you spotted it there, congrats! My revised trace starts the collapse right there, with the pair. Here’s the whole thing:

Next time, checkpoints on 254, the bypass fatality on the left, and holdout 338, on the right.








After a timely multiple solutions report, the review of Only Extreme Sudoku continues.

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AIC Slinks Finish Only Extreme 3

This post continues the finishing coloring cluster expansion in Castillo’s Only Extreme 3, via not-both testing of AIC slinks.  After extending the blue/green cluster in the North bank via AIC slink, we continue with a second AIC slink adjoining the cluster, shown below.

If 1r5c5 and 2r5c8 both true, we could declare green false, blue candidates true, and be almost home. If not, the burgundy slink is also a coloring link, and blue/green expands.

The both-true combination forces two 3’s into c6.

The cluster expansion traps 67r5c4, but more importantly, it enables a third AIC slink to apply for a coloring license.

In the olive AIC slink 2288, if both terminals 2r5c4 and 8r4c7 are true, blue is confirmed, but along with that,  all three 8’s are removed from the South box. So 8r4c7 is green, and coloring makes a leap.






Traps along c8 and r5 are first, then the 8 removal in r5c6 creates a naked triple. In the North box, only the 5 sees all of its peers in the triple. The 6 and 7 candidates do not, because the triple is defined in the c6 column, not the N box.

After  a brief marking,





The blue confirmation finishes Manuel Castillo’s Only Extreme 3.

Certainly a puzzle requiring three not-both extensions of the coloring network (and two posts) deserves the extreme grade.




I will review the Only Extreme collection by preselecting these 10:   3, 46, 89, . . ., 385 in case you want to get there first. 

Before that, however,  let’s look at Only Hard Sudoku, Manuel’s earlier collection of basic Sudoku, that came out in 2014. Next week,  we’ll have the review table, and Only Hard 128, an unusual case of a box marking collapse triggered by hidden pair not accompanied by a naked triple.  Can you do the  Sysudoku basic without letting the hidden pair slip by?

 Next Monday, I’m doing an introduction to Sudoku for the Fairlawn Ohio Senior Club. I’ll report what I did and how it went, in case you might consider doing that. 




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Cluster Extension by Not-Both Trials

In this post and the next, the first puzzle of the Manuel Castillo Only Extreme Sudoku review, Only Extreme 3,  is taken ahead of the review of his Only Hard Sudoku. The reason is in the title. Rounding out the discussion of AIC slink, here they expand a coloring cluster. It requires the confirmation of their not-both conditions. This turns out to be a task suited to the trial trace developed for Sysudoku monster slaying.

To checkpoint your head start on Only Extreme 3, here is the basic trace and line marked grid. The trace is short because it reflects the help you’re given in basic, which isn’t much.

It’s enough to signal that this review is going to be tough. If you didn’t already try it, maybe you’d like to survey the line marked grid to see if you can find something more basic than the bv scan stretch I have for you below.



The bv field being limited and uncoordinated for XY-chains, I worked extra hard for XYZ-wings, and found this i786-wing:  one wing is attached to the hinge by a grouped 8-chain wink. The victim sees that wing’s Z=6 by forcing chain, or if you prefer, ER.





The X-panels were very imbalanced, but I closed one side of a skyscraper with a 1-slink for a productive AIC nice loop.



These removals allowed me two more nibbles, a finned 5-wing and a 4-chain ANL.









Even better action comes with an old friend I seldom get to use, the Sue de Coq.  In this one, the contents of chute Wr4 is described as 2(4+5)(6+7).

Within the West box, the bv 67 must supply the missing 6 or 7, so the extra 7 has to go.

Now there seems to be enough coloring action among the 1’s, and the dead 4-wing to get something going. Two AIC slinks are in position to expand the blue/green cluster.  In each case, the uncolored slink partner colors differently, depending on the not-both condition.

Testing the not-both for the aqua slink, the trial trace reveals that if 8r2c3 and 1r2c5 are both true, no only is green confirmed, but two 5’s are forced into r1. The arrows show the direct paths to this conflict. With not-both the cluster expands, trapping 5r2c8.



After the cluster expands to the 8’s of the North bank, 8r9c3 traps itself by  finding a way to see the green 8r5c5, as well as the newly colored blue 8 in c3.







After the naked pair c3np45, there is a 5-wing, and some further cluster expansion to do.

Want to take charge? Take over with the  not-both test of the burgundy AIC slink, and compare with my continuation next week.

This post is long enough.







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Badger’s Advanced Sudoku

This post highlights David Badger’s two advance puzzles in the Sudoku 1001 Hard Puzzles sysudokie review, both starting with the almost nice loops to be found along the XY railway.

In 301, the black XY ANL removes two 7’s, and the red extension ANL, two more.


The extra bv allow the XY railway to expand. Coloring extends along a (red) spur in the North box.





The cluster traps 4’s in N and C boxes, and the extension coloring wraps green, confirming blue for the collapse.  



Turning to 101, there’s a weak bypass, and relatively difficult box and line markings, with columns heavily favored over rows.


An indecisive ALS/XZ turns up in the bv scan, but I found nothing else.







On the X-panels, a 4-chain organized the 4’s of the North bank by box/line interaction.








The removal of 4r2c6 enables a 361-wing with an i-wink  victim. It sees the third 1 of the wing by forcing chain.








Plenty of bv for coloring. But the slinks are divided among three clusters. Fortunately in the red/orange cluster, 5r7c5 is found guilty of generating two more 16 bv in the Center box, to go along with the one already in place. The 5r7c5 removal would be decisive in itself, but with the coloring it wraps orange, which, as shown by the arrows, confirms green and violet.

The bottom line on David Badger’s huge collection, his foray into “ordinary Sudoku”, is a constantly entertaining basic level, and a challenging advanced level, if you have the patience to get there.

You never know what the next puzzle is going to be. Kinda’ like the Arabian 1001 nights.

Next time, I jump ahead of myself to preview a review, by taking on Manuel Castillo’s Only Extreme 3. It’s an opportunity to say one more thing about the AIC slink. You may find a way to skirt the trials featured in this post.

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