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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 andrew@str8ts.com.

Post a Comment or Question here...

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Any Sudoku you want to publish here for easy loading into the solver - Either 81 numbers or the packed string version.

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Comment, question or feedback:

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If you are writing to alert me of a problem (thank-you!) please include a url to the page in question.
Can get fixes in quicker if I know immediately where to go.

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

Thursday 11-Sep-2025

... by: TenPeter, USA

Load Sudoku: CLICK TO LOAD

New version 2.40.2 has some sort of bug in the solver. The above puzzle is the first in the 2.2M puzzle database. The first step is an Exocet. There is an hidden Tridagon in the puzzle that has a valid pattern in Block 0. If the triplet is removed from A3 leaving 45, the "solution count" does not flag it as an incorrect value but setting cell to either 4 or 5 does get flagged as no solution. The correct solution for the cell is 1. In the case of setting cell to 45, the returned solution is the correct one.
Also it is not possible in 2.40.2 to copy the solution from the "solution count" window.

I looked at the Exocet question from Ayumu below. The pattern is not an Exocet as it violates the cover house pattern rule for digit 8. This would imply that 8 can not be a base pair nor a target digit. Removing the 8 from those cells results a proper detection by the solver of single Exocet. The second Exocet has the same cover house issue as well as invalid companion cells.

Andrew Stuart writes:

Thanks for the bug report on copying from the solution count popup. Just fixed that now.

Regards the solution count I can explain the behaviour by stating that the solution count works off clues and solved cells. Not the current candidate spread. I pass in an 81 character string so its one digit per cell. I can see the utility of checking for a solution count based on the current spread. 99.9% of the time there will be no difference as the candidates conflicting with solved/clues are flashed removed on the first step in SC. But I suppose if you are pecking way at candidates it’s a way of checking you didn’t remove a solution
I might add that to the job queue. Guess it will need some kind of checkbox.

Possible there is a problem with the very limited rule set I have for exocet. I have never had a false positive yet so I assumed I wasn’t making a mistake. But I need to go back to exocet and look at the whole thing again. Probablu after Tridagons which I need to look at first
Cheers

Ayumu writes
Reply for TenPeter in THURSDAY 11-SEP-2025 post:
Hello, I don't know why do you think 8 is not a valid number, 8 can only appear twice in CL, one is in c3, another is c7. load puzzle
Here is a img from YZF_sudoku, a sudoku program with exocet.
https://img.cdn1.vip/i/68ce272de010d_1758340909.webp
https://img.cdn1.vip/i/68ce28a4480b6_1758341284.webp
The img show the exocet with my original exocet and double exocet.
You can find yzf_sodoku from http://forum.enjoysudoku.com/yzf-sudoku-t36846.html
Welcome to furture discussion.

Wednesday 10-Sep-2025

... by: Handle, Water

Dead Mr. Straits,

unfortunately I'm too dumb to understand some of these great explanations of diabolical, extreme etc. strategies.

Would it be possible to make puzzles where you learn these strategies interactively and with a focussed way, e. g. you're presented with situations where the specific strategy applies and have to solve them yourself, step by step?

Thank you so much!
Bridge Troll

Andrew Stuart writes:

I'm sure you're not. And yes the more complex strategies are of interest to programmers really although some people have told me they pen and paper them. But you can find “exemplars” at the bottom of most documentation pages which are trivial apart from the strategy for that page. Also, pick moderately difficult puzzles and then try the three hint modes (next to “take step”). Use Take Step until an interesting point is reached. Three hint modes: you can be presented with the pattern – find the elimination, or the elimination – find the pattern; or just the strategy name – find the pattern AND the elimination.

Monday 8-Sep-2025

... by: H, Sweden

Why does the solver auto remove numbers repeated in the two diagonals?

Andrew Stuart writes:

What solver? Should only be on Sudoku X. Drop me an email address so I can reply directly.

Monday 25-Aug-2025

... by: David, Hong Kong

I like the new format but after building the cages I cannot figure out how to enter the clues. It was easy in the old version,

Andrew Stuart writes:

Click on the blue button "Step 2". I had to split the two tasks as the operations were too complicated for so many different devices.

Wednesday 20-Aug-2025

... by: DavidC, USA

Hello Andrew, the various examples that you provide often have two links: "Load Example", and "From the Start". It seems that "Load Example" is identical to "From the Start" and thus the state of the example (solved cells vs. clue cells, and candidates) isn't reproducible. I think the links were different in the recent past where "Load Example" would have a longer string starting with "S9B".

Andrew Stuart writes:

I do have a job to go through the examples and replace the old string with the new one so the example loads directly. Been “as and when” so far. They should be distinct however.

Thursday 14-Aug-2025

... by: Tony Payne, United Kingdom

Hi neighbour
Is it an intended "feature" of this website that I was asked to confirm my cookie choices twice? ;o)
First on https://www.sudokuwiki.org/
Second on https://www.str8ts.com/Daily_str8ts
Didn't happen when I went back into the site

Andrew Stuart writes:

I think it's necessary now. I don’t have cross-domain cookies and the browsers don't like it when I try, so that’s where we are I'm afraid. Different sites, click again

Monday 11-Aug-2025

... by: Mark, WV

Re: 6x6 KenDoku Solver- Sample 38

Grader gives "Empty cell: E6"
Due to that the Solve Path ends up broken.
Going step by step, when it comes to E6, it takes out all numbers in D6 resulting in a "0" for the cell solution.

Andrew Stuart writes:

Thanks for the report Mark
Simplest is to delete that sample puzzle which I've now done
Refresh

Saturday 9-Aug-2025

... by: Bob, Russia

The solver page (/sudoku.aspx) is behaving in a very strange way being open on Samsung Internet browser (Galaxy S22+). Many buttons don't work at all (such as Email to a friend, Solve path etc.). Disclaimer in a box under the playfield claims to update to version 2.35 <> 2.37, while this mobile browser has neither keyboard (for Ctrl+F5) nor an option to clear specific site cashes. Please add a UI button for site update action.

Andrew Stuart writes:

Hi Bob. Yes that script should not have been there. I sometimes upload it to test but the real solver is sudoku.htm. I've deleted sudoku.aspx

Wednesday 6-Aug-2025

... by: Charp, Canada

Hi there. The st8ts main page hasn't been loading properly for me for a few days on my laptop in firefox.
https://www.str8ts.com/
Is the issue happening on your end or mine? Missing my daily asymmetrical st8ts!
Thanks

Andrew Stuart writes:

Seems okay to me. Is it persisting in not showing? Add an email address so I can reply directly.

Monday 21-Jul-2025

... by: Antonia Natale, Denver CO

Andrew: A friend of mine just showed me your Sudoku app and I really loved it. However, I have an iPad. Do you have a workaround for your app to run on Apple devices or plans to create an Apple compatible version?

Thanks!

Andrew Stuart writes:

I'm afraid I don't own a Mac and therefore can't run XCode and therefore can't create Apple Apps. The 5 Daily Puzzle app is going to get delisted soon for the same reason. Something I'd like to change , we'll have to see.

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Thank-you everyone for all your questions and contributions.