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Feedback and Questions

I've received a lot of interesting comments and questions from Sudoku fans over the last few years and this page is where I try to answer them. I'm also directing Str8ts feedback here. Please feel free to drop me a note on the side of the page. Or you can email me directly at .


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Many thanks to all the people who have helped improve the solvers and strategies with their feedback!

Tuesday 21-Mar-2023

... by: André, Germany

Hello, great site you have here.
I came here to get some informations about the Setti-rule of Str8ts. Your article helped me a lot to understand it, but I don't see it exactly in your example with "Extreme number 31".
You say, that you are sure, that in every column there has to be a six. But column 9 would work without a 6 right?
Maybe I don't see it but this confuses me.
Anyway, thanks for all the hints and tips on this site!!!

Andrew Stuart writes:

To be honest I barely understand Setti myself. I know I didn't finish the article and I'm hoping someone can help me write a better one. However plenty of people in the comments for the weekly do seen to know it very well, can try and ask there
Sorry for such a lame answer!

Monday 20-Mar-2023

... by: Doug Fraser, Canada

Load Sudoku:

This is an "extreme" puzzle, created by my generator, solved in 51 steps by the solver, employing tools: Alternating Inference Chains (10 times), Hidden Unique Rectangles (3 times),Aligned Pair exclusion (twice) plus Digit Forcing Chain, X-Cycle, WXYZ Wing. When I try to disable the latter two (to see if the puzzle remains solvable anyway) - the disable does not seem to take and I get the same 51 step solution path, employing those tools in the same steps.
Did I miss something?

Andrew Stuart writes:

Talking about "Solve Path"?
That uses all strategies. Ticks are for the solver only. Could be something I should make a feature

Saturday 18-Mar-2023

... by: Andy, USA

The daily of 2023-03-18, difficulty 5/6, was an entertaining puzzle. First, I made a dum mistke but was able to back out of it a dozen moves after the fact, and you know how frustrating and then satisfying that is. Second, after solving down to confetti, all little numbers, I soon recognized a potential ambiguity spanning 9 cells, and all I had to do was avoid it to solve out quickly, and you know how satisfying it is to apply an abstract meta rule. SudokuGuy on youtube refers to this concept as "Danger", and he's quite entertaining in a Mr. Rogers sorta way, so which see. Actually, the cleanest way of looking at a Sudoku puzzle is that what we're actually doing is proving, by example, that the clues specify a single populated Sudoku board. Usually, the steps are cell-wise elimination, but "Danger" is puzzle-wise elimination. Whatever ingredients went into this puzzle, it came out yummy, challenging but not tedious, looking forward to more like it. Thanks!

Andrew Stuart writes:

Glad you enjoyed and interesting breakdown, thanks!

Monday 13-Mar-2023

... by: maritza, Spain , EU

Thank you. What an enormous amount of work you have done!

Andrew Stuart writes:

Cheers! Appreciated, glad you find it useful

Monday 20-Feb-2023

... by: Chris Wray, USA

In Safari, the solve path window never appears for me. Works fine in Chrome.

Andrew Stuart writes:

I've checked on my wife's iPad and I can see the problem. Safari blocks popups but I've used and alternative. It does not open in a new tab like on Windows so you'll need to use the browser "back" button to get back to the solver.

Made some css tidyups as well

Friday 17-Feb-2023

... by: Nabl, Netherlands

Load Puzzle

There is a X wing in this puzzle for 4s. It is not recognized

Andrew Stuart writes:

Can't see it. More details?

Friday 3-Feb-2023

... by: Béryl, France

Hello! I've discovered your site a week ago and I love it! I've been trying to use it to teach myself how to learn methods. I want to enter possibilities by myself and only when stuck use the solver. However when I enter only one possibility in a cell, it shows up as the answer for the cell. I work number by number in all the grid and not cell by cell so it's just temporary to have one possibility, i'll write others when I'll search for other numbers. Is there anyway that I haven't found yet or is it just not the right logic to solve Sudoku? Thank you for you help!

Andrew Stuart writes:

The solver needs to control the candidate spread if you are using "Take step"
I suggest you use "Player >" to send the puzzle to the player which does allow candidate editing
And if you get stuck "send to solver"
The solver will still ignore your candidates since it needs all logically present ones, not just the ones important to you. But you can step from that point to discover the strategy

Tuesday 31-Jan-2023

... by: Angelika, Germany

Hallo again,
Sorry, I need help again:
When I want to print a str8ts puzzle, the black squares are not there. How can a get them?
Thanks and have a nice day.
Angelika

Andrew Stuart writes:

When you get the printer choice dialog box - tick "Print Background-images" in the print options.

Tuesday 24-Jan-2023

... by: Mary Clark, Canada

FYI, I just completed the Daily Str8ts and filled in all the cells but I had a mistake. No error messages came up. I fixed the cell and then got the Congrats message.
In the previous version, as soon as all the cells were filled in, the number of errors would be reported.

Andrew Stuart writes:

Doh! Yes there was a typo in the code. Fixed now, version 2.15
Many thanks for letting me know, appreciated

Monday 16-Jan-2023

... by: Terje, Norway

Reported a bug on sheet. Seems to work normal again. Love this sheet and have used it for years loading hard puzzles and doing step 1 and 2 before printing.

Andrew Stuart writes:

No clear what page you are referring to. I was just now fixing something on the sudoku player which might have broken it for 10 minutes. Also - please send email so I can respond directly
Page:2023 1 2 3 :2022 2021 2020 2019 2018 2017
2015 2014 2013 2012 2011 2010 2009 2008 2007 2006
Thank-you everyone for all your questions and contributions.