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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A Pink Pattern Trial on Insane 495

LPO is delayed one post in the Sudokuwiki aided update of the KD Insane review, because two more effective methods are highlighted in KD Insane 495 of 10/08/13. A second ALS boomerang turns up, and after a similar pattern analysis isolates two orphans on the 5-panel, a trial of the 3 pink patterns on the 8-panel decides which candidate of the boomerang’s ALS 8-group is true, and continues to the solution.

Here is the freeform that demonstrates how a dumbfounding announcement by Sudokuwiki can be humanly verified. It was that 5r9c9 is an orphan, i.e. it belongs to no 5-pattern. That hits anyone defeated by twisted jungles of freeforms where it hurts, especially when looking at such an X-panel. But then, when you see that the South box claims the only remaining r8 5, and SW must have the r7 5, you’re more prepared to look at how far this goes. And it’s not far.

The announcement orphaned 5r7c  as well, so before looking at the 2013 post, you can freeform your way to that conclusion. We both can remember to check  three line banks or towers to see what gets through.

Now in a puzzle saturated with 8’s Sudowiki demonstrates that a cloud of candidates can have weaknesses. Two ANL strung together eliminate two from a column of eight. One uses  an ALS 8-group as a slink chain terminal.

Then we get the second ALS boomerang ANL in this series.  An ALS 8-group and a candidate member are terminals of the slink chain, confirming the group contains a true candidate.


Then when Sudokuwiki retires to a neutral corner to catch a breath, I pile on with a pink olive move very similar to the 5 orphan eliminations above.

Here are the 8-candidates that are left.  The two members of the ALS 8-group are involved in a pink olive slicing that is smothered in candidates. However there are only three patterns that follow the pink slice established in the first three lines. In a trial of these three patterns, 13 orphan 8-candidates are removed, and new clues and bv are created by the removals. That means the likelihood of a solution or a contradiction is very high. Either one is a large advance. A contradiction would remove at least the three pink candidates and create at least six clues. Both of these prior facts are evident in the grid as the trial begins.

In the trace to the solution, you can see where the continuing collapse is dependent on one clue. And as you step through the trial, you can see the near ambiguities that make Insane puzzles so hard.

Next report is on the update of KrazyDad Insane volume 4, book 10, number 5.  Sorry about bypassing the LPO examples in 495, but 4×5 fills in for a process demonstration. There are other places where it is more needed, and more decisive.

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Sudokuwiki Gets a Second Chance

In a second updated review post on KrazyDad v.4, b.8, n.5 , Andrew Stuart’s Sudokuwiki solver gets the clue that the ALS boomerang left unresolved, and finishes the solution, with more instructive moves. You get a shot at that unusual clue.

Here is the 9-panel when KD 485’s ALS boomer discovers that 9r2c2 and 9r2c9 are a toxic set. It looks unpromising, until you take the toxic set into account.  Do that for yourself, then enjoy  the parade of Sudokuwiki moves in the updated post. There’s a BARN, an unaligned APE, and classic 263-wing.




A particularly impressive move is this ALS aided confirming ANL promoting  9r5c4. For you or me, it could have started as a possible boomerang, leaving 9r5c4 in search of a wink back into 1 to eliminate that 1. But since the cell is a bv, it also puts two slinks around 9. Actually it’s the same result, whether you list it as a confirming or eliminating ANL. With another candidate in the starting cell, it would be only eliminating.

When the solver invokes coloring for a single trap on 3r4c3, we expand the cluster as far as it will go, in pursuit of a possible wrap.  The 363-wing and Wr6 boxline elimination are reported on the same grid.  The wrap is not long in coming.

The next update report is on KD Insane 495, already up.

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