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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Reviewing James Forest’s Classic Sudoku

This post presents a Sysudoku solution of the Classic 24, from James Forest’s Book 30. We’ll do every 24th Classic. The first suggests an easy basic and an interesting diversity of advanced methods.

The bypass fills the East boxes with 20 placements, including naked pairs and two immediately resolved 3-fills.

How many UR signposts are there among the naked pairs in this line marked grid?

Out of five naked pairs, three possible UR’s call for a closer look, for Type 2b.

The same bv are also covered in an unproductive scan for Sue de Coq.





The UR is there.

On the bv map, no ANL, but the single i471-wing defines a toxic set.  No victims, but we can  leave the toxic set markers on the grid copies, as we move on to the X-panels.





The 4-panel closes Classic 24 out with a finned swordfish. 4r6c1 is the fin, and the removal of 4r4c2 in the fin box brings in C4 and the collapse. It turns out that two of the toxic set members are true.






Next time, James Forest’s Classic 48 will carry us further along. Can you say just how far?

The Guide pages on the Unique Rectangle and AIC Building are updated.




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KD Insane 4×5 Caps the Review

KrazyDad Insane v.4, b.10, n.5, the last of the Insane review of 2013 is updated, with findings by Andrew Stuarts Sudokuwiki solver and YT. The solver gives us one of Andrew’s Type 2b UR, an ALS boomerang ANL, and something new, a nest of boomerangs. I continue with a walk through of LPO and a pattern trial that eliminates two patterns of a slice, leaving only the follow up of the revealed pattern.

After a generous bypass, KD Insane 4×5 starts with an overabundance of 1,8 and 9-candidates. If you haven’t looked at the updated post yet, find the Type 2b unique rectangle. There’s a floor to ceiling slink . The Solving Tools page has a UR chart.


Next, 4×5 goes directly to AIC building with a series of boomerangs that fit on one grid, because all but the first is an extension of another. The common infrastructure is an ALS that stays in the path as the solver keeps reaching back to an earlier and earlier starting point.  Directions come with it, if you’re like me, assemble first and read later.

Sudokuwiki treats these as separate findings, each one enabling the last.

Unwilling to be left out, 4×5 had to provide Sudokuwiki an ALS boomerang ANL.  The 8-group of the ALS is one terminal, and group member 8r1c7 is the other terminal. The 8-group has to contain a true 8.

This time, when Sydokuwiki gives up, it’s time to do the freeforms and lettering on four X-panels of Insane 4×5 for a Limited Pattern Overlay, covering X = 3, 4, 5, and 6, with 3, 3, 6, and 4 patterns respectively. Also included is the 7-panel with 2 patterns in a single 7-wing.

The idea is to discover any patterns eliminated, with corresponding candidate eliminations, due to conflicts between patterns. It takes organization, because a pattern is not eliminated unless it conflicts with every pattern of another value. To begin, we have to name every possible pattern of the participating values.

Now every cell of each pattern is examined for conflicts with other values, to be translated into conflicts with patterns of other values.

It’s a Big Data problem, the kind normally done by computer, barely kept humanly possible be restricting the data.

The 2013 post illustrates the conflict tables that keep the books as the scanning is done and gives the readout of eliminated patterns.  It doesn’t quite work on 4×5, but it sometimes does. The process qualifies as a logical solution, as opposed to a trial.

In earlier Insanes, coloring trials were set up with apparent clusters made up of pairs of patterns, effectively testing two patterns at a time. Doing that on the 4-panel, with 3 patterns, the true pattern will eliminate a false pattern paired with it, so a contradiction eliminates both patterns.

One trial, on 4a and 4b reached a contradiction in a lengthy trial, leaving 4c to be installed as the true pattern. One color is wrapped in the follow up, and when it stalls, a remote pair and a lengthy XY-chain ANL collapse all resistance to the solution.

The updated review table, with which you can compare the Insane collection to others reviewed in Sysudoku, is in the post of 10/22/2013.

Next post will have parting comments on contributions of the Insanes to the Sysudoku Guide, and an introduction to the next collection review, Classic Sudoku, Book 30 by James Forest. The review starts with Classic 24 above, and includes every 24th for the preselected 10 review puzzles. Have your version ready.


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