Classic 192 and Updated Only Extreme 3

First, a Basic trace of Classic 192. It can be solved in the bypass. In this post, James Forest’s Classic 192 is traced down in Basic. Then there’s a second Advanced level solution of Manuel Castillo’s Only Extreme 3, the first puzzle in the Only Extreme review. In the review, OnEx 3 was solved by not-both trials which promote an AIC slink chain – having slinks at each terminal – into a coloring link. The review was an occasion to demonstrate this tactic as a last resort, but with refinements introduced in Sysudoku AIC building, several of the Only Extreme “not-both” puzzles,  including OnEx 3 are solved without trial. An Advanced level solution of OnEx 3 appeared in the post of 10/3/17.  The second one of this post uses some interesting Sudokuwiki moves.

First, a Basic trace of Classic 192. It can be solved in the bypass.



For the Advanced level resolution of Only Extreme 3, start with the Basic grid and trace posted on August 29, 2017.

This time, right out of the hidden pair line marked grid, Andrew Stuart’s Sudokuwiki found a BARN, a.k.a. Bent Almost Restricted n-Set. After the BARN, the i186-wing, 4-chain, finned 5-wing and Wr4 Sue de Coq, still apply.

Then on the 6-panel a grouped nice loop takes out three 6-candidates.









An 8-chain triggers a naked pair.










In AIC building, two reverse bv support a confirming ANL.









The follow up marking includes a hidden dublex.



Coloring may be overdue. The blue/green cluster expands with two traps, with follow up marking.








This leads to three more traps, with follow up marking




Blue is confirmed, and the solution is immediate.








Next is Basic level Classic 216 and a report on the update of Only Extreme 132, originally posted 10/24/17. The pattern analysis that rescues an indecisive not-both trial now solves OnEx 132 without trials.

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Classic 168 and Updated Only Extreme 89

James Forest’s Classic Sudoku 168 is a Basic level challenge.  In this post, the Classic review is continued with the 168 box marked grid, and a basic trace carrying through the collapse on the second line of line marking. Then a report is given on the update of Manuel Castillo’s Only Extreme Sudoku 89, at its original post of October 17, 2017. Think of it as an invitation to get back into early posts.

The Classic 168 box marked grid has four lines marked, and four free cells in four more lines.

The middle line in the trace below is the box marking. Below that is every move, in order, of the collapse of Classic 168 into a solution, on the second line, column 1 of line marking.



It may be difficult for casual readers to realize what the trace is. The Guide pages will open the trace, and systematic Sudoku, to anyone.

Now about the review of Manuel Castillo’s Only Extreme Sudoku. It’s the second collection review selected for update, after KrazyDad’s Insane collection. These updates are undertaken on the hardest puzzles, and are reworked with backup from the Sudokuwiki solver available to everyone on Andrew Stuart’s site.

The original post of 10/17/17 solved Only Extreme 89 by a Single Alternate Sue de Coq, a Sysudoku trial innovation. Then it was shown that a freeform pattern analysis on one X-panel put four patterns in the pink slice and only one in the olive slice, and that the key clue isolated by the SASdC belongs to the single pattern. Either trial solves OnEx 89

The update solves OnEx 89 without trial, by full use of AIC building, including the recently recognized boomerang type of ANL.

Gratifying but not significant for the solution was this BARN, or Bent Naked Almost Restricted 4-set. BARNs are one of the friendly interpretive disputes between Sysudoku and Andrew Stuart.

Sudokuwiki found it and I didn’t, but stretching the definition of the WXYZ-wing to cover it, as the solver notes do, is not helping anyone to spot it.

At the bottom here is the SASdC. It’s logic is explained in the updated post.

After an easy finned X-wing and a 12-link  boomerang, this ALS node eliminating ANL and an ALS node confirming ANL, or boomerang if you prefer,  bring a respectably logical collapse.

C’mon, you have to look.




Next in the Classic review is 192 at right, and an updated solution of Castillo’s Only Extreme 3 below, originally posted 8/29/2017, where it demonstrates trials to extend coloring clusters onto slinked AIC segments. The updated solution avoids trials.




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A Colorful Finish on Classic 144

This post continues the solution of James Forest’s Classical Sudoku 144.

The boomer parade pauses for a pair of AIC  ANL.  This one uses reversed bv to switch from 2-chain to 8-chain and back again.







On the same base, the top is shifted for a second ANL.





Sudokuwiki adds one more boomer, a grouped one,  that produces  two naked pairs.












As the first cluster is added, Sudokuwiki finds a confirming AIC ANL.

The follow up marking







creates an ample field of bv for a second cluster.

The red/orange cluster is no sooner created, than wrapped by a newly created 798-wing. An orange 8r7c2 sees the toxic set, and the red candidates  lead the collapse.

After all those boomerangs, an XYZ-wing?  That’s Sudoku.



Next up in the review is Classic 168, shown here. The remaining four pre-selected review Lpuzzles are resolved in Basic.  For that reason,  basic traces of remaining Classic  puzzles will be combined with reports on updated posts from Manuel Castillo’s Only Extreme Sudoku.  Next week, the first update report is on Only Extreme 89, originally posted 10/17/2017.

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A Classic Insane 144

After the two Basic level 96 and 120, James Forest’s Classic Sudoku comes back with one puzzle, 144,  in the tradition of the KrazyDad Insane collection.  The bv are there, but it takes a few X-chain ANL to jar loose a couple of APE for the bv scan. Then AIC building brings a long stream of Sudowiki boomers, finally ending with a line slinked cluster, which is immediately wrapped by an AIC confirming ANL. A second, more extensive cluster is then wrapped by a late emerging XYZ-wing.

Your first checkpoint is this grid as box marking ends. A built-up naked triple is left for the marking of four rows to follow.


Line marking is tough, even with the naked triple and a hidden pair removing four candidates in r5c1.

The first two Advanced moves are simple X-chain ANL. They’re superimposed on the line marked grid.

A Sudowiki follow up is this APE worthy of a Guide example. Restrictions on red cell pairings include a separated ALS in c8, taking out the 27 pairing, joining the 79 pairing to remove 7r3c8.







After this hidden single follow up,




a grouped 2-chain ANL rounds out the X-panel attack.










The removal supports another APE defining example, allowing a box ALS to participate.

Coloring doesn’t get started here, so its time for AIC building.


The KrazyDad Insane update showed that AIC hinges are not used frequently enough to mark ahead of AIC building. Cell winks of other kinds are too often useful to have the pre-drawn AIC hinges distract attention from them.

In Boomer 1 the 3-slink emerging from r1c7 is an XY-chain.


Boomerangs 2 and 3 start with the 8-chain out of r2c6, with XY transitions to 2 and then to 6. One returns to 6r2c6. The other, to XY to see 3.

The first AIC boomer is the fourth, with the 5-slink AIC using an AIC hinge and two reverse bv to go to 4, 5 and 9 into starting cell r7c1.

Boomer 5 emerges on 5 and XY-chains to 1 and 6, and 6-chains on back to the starting cell r1c6.







The same chain is used in a back up boomer 6, starting with a 4 from cell r1c4.








Going back one, boomer 5’s 6r1c6 removal adds a second slink for this hidden unique rectangle, Type 1. If 2r7c6 is true, the slinks force 6 in the two adjacent corners and 2 in the opposite corner, a composer’s nightmare.

Let’s pause for an opportunity for you to finish Classic 144 your way. There’s plenty of action left.

Next post, this report continues AIC building a few more eliminations, then builds and wraps two coloring clusters.

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Classic 96 and 120 Solved in Basic

In the James Forest Classic Sudoku review, The next two pre-selected puzzles are solved in Basic, one in early line marking and one in the bypass. They are both excellent examples of the kind of Sudoku entertainment Basic level puzzles provide.

With Classic 93, the bypass was over quickly and box marking completed the 9’s. Then three lines in, a hidden single starts a rapid collapse. Along the way, you see a chain of identical bv 38 develop and collapse before reaching remote pair length.

Here is the grid, just after the naked single and hidden single, and just as the collapse is starting. Following a collapse, like box marking and line marketing, is a routine activity. But it is also satisfying, like knitting and whittling. The trace looks complicated to the uninitiated.  But it builds itself, with simple, efficient steps.


On Classic 120, we have only the bypass to report. The trace spreads across the page, before dropping in the collapse, leaving many causes unused.


For Advanced only readers, Forest’s Classic 144 is worth waiting for. It requires a parade of boomerangs, and has a surprising Sysudoku finish.

After that, the Classic review finishes in Basic, along with reports updating another review . If you have a needed update in mind, let me know in a comment.

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An XY Playground in Classic 72

James Forest’s Classic 72 delivers two rare birds, then gets tripped up by a Y-wing.

The bypass threatens to take over, but leaves  an XY playground.




The line marked grid gives all of the Sysudoku Basic results.

Two fill strings of one value is a bit unusual.

The generous bv field predicts a productive XY railway system.




But first we look for UR, SdC, APE, and other methods not requiring maps and panels.

Here we have a classic indeed, an ALS toxic pair. The 3 value is contested, but 8r5c9 sees both groups of 8 that would be locked in by the winner.


Significantly, a 4-value Bent Almost Restricted n-Set, a BARN, can be superimposed around the ALS pair. Only the 8 values are bent. The removal is not as significant.

The significant removal is 6r1c4. It’s a 3-node XY-chain, adding  an NEr1 boxline removal and a naked triple in c4.

Collapse is immediate.






Next is Classic 96 (left) and 120. Both are solved in Basic.  Have your versions ready.




The Guide pages Sysudoku Basic, and Begin With the Bypass have been updated. If you’ve been putting off a serious evaluation, now is a good time.

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Classic 48 Gets to the Crayons

The second Classic of Forest’s Classic Sudoku book 30 is a strategic win for Sysudoku Advanced. X-panel keys unlock an imbalanced web of 3, 6 and 8 candidates, allowing coloring clusters to carve it into four armies, which merge and wrap promptly.

Many placements are made in the bypass and in line marking, but with many unsatisfied 3-fills. Tracing it out, you can add  8-wing markers to prevent the addition of wing victims to the grid.


The grid with these markers reveals an imbalance of values , with 3, 6 and 8 predominating.








X-wings are spotted with routine checks in line marking, but finned X-wings  show up on an X-panel. Analyzing for both as each X-panel is completed, this fish and X-chain are spotted at the same time.





In this case, the X-panel jumps ahead of the bv map, adding a central bv to this XY network. There just has to be a way to connect a remote pair chain of at least four, and there is.









It takes a little follow up to get to the remote pair.



Now we can lay on a healthy blue/green cluster and still throw a red/orange one over the 36 bv.

Common values show that

Not(red and green) =>      orange or blue.

In cell r5c6, this fact traps 3, allowing a slink to merge red and blue, along with orange and green.

In the merged cluster, the trap in r1c2 => NW4 => SW3 wraps blue, and the solution is full of little green men.


Next week, be ready with your Classic 72. James Forest wants you to get the most from his other 240 puzzles. You may have two bv scan rewards right out of the line marking gate.





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