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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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Any Sudoku you want to publish here for easy loading into the solver - 81 characters, use '.' or '0' for unknowns.

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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!

Friday 30-May-2025

... by: Timko259, USA

I have played with your newer version of sudoku now for about a month. I am not in favor of the change you made to cause me to move the cursor after entering a number. This is unnecessary. I prefer the previous method where the cursor automatically advanced to the next slot after entering a choice. This recent change is tedious and unnecessary. As one who has been using this site for a long time, please consider changing this back.

A very loyal user.

Dale

Andrew Stuart writes:
Referring to the small board number entry on the solver?
Is “Auto tab” ticked? For some reason the browsers have adopted a new policy on cookies and this may have been deleted. I hope it sticks if ticked again.

Friday 23-May-2025

... by: A random stranger, Earth

Just a heads up, the "Check" button of the sudoku player doesn't seem to work correctly (at least for custom puzzles), e.g. when you open and immediately click "Check" the player reports the nonsensical "Oops! There are -33 cells which are wrong." Happens both with the packed string and the 81-digits-variant.

Andrew Stuart writes:
Good bug report. Yes if no solution is available the check will be nonsense. Imported puzzles don't have a solution. I've updated it to v2.34 and put in a sanity check and notice. Thanks for the alert.

Tuesday 20-May-2025

... by: Peter Brown, San Diego, California

Load Sudoku:

Small feedback - As you know, when multiple chains are found in the solver, it's nice to be able to explore each one using the left and right arrows.

Sometimes, when you select the next button, the content above the arrows (describing the chain) will have more or less lines, causing the location of the next/prev chain buttons to move.

So, if I want to click through and view each chain, I can't simple keep clicking to see the next chain. I must click, view the chain, then move my mouse to find the button to view the next chain since it might have moved.

It's just a small piece of feedback that could slightly improve the user experience. One solution would be to move the chain browsing buttons above the content describing the current chain in view. That way, the dynamic content can freely change height, without effecting the location of the Next/Prev buttons.

Andrew Stuart writes:
An excellent suggestion! I have implemented it just now. Hopefully a simple page refresh will show it, otherwise [CRTL]+[F5]

Wednesday 14-May-2025

... by: Barbara H, Outside Chicago

I wrote last week complaining that the Str8ts solver loaded correctly but then turned into a completely black page after about 3 seconds. (Android tablet.) Well, that's still true but I just needed more patience. Today the black page turned back into the puzzle about 2 minutes later. Seems like a long time for the page to finish loading. But it did load!

Andrew Stuart writes:
Excellent. If anyone else, let me know

Sunday 11-May-2025

... by: PAUL DAYNES, NEW ZEALAND

I came across this one on YouTube. Your solver does not complete it and at one point the solution count is 26. However, the YouTube poster has a method that does solve it and you may like to investigate this method. https://www.youtube.com/watch?v=m9Xaa4GXs9I

Andrew Stuart writes:
Thanks Paul. I looked and an interesting strategy. I will have to add it. Not sure how useful it will be but a card in the hand for sure

Wednesday 7-May-2025

... by: fabrizio, italy

hi andrew,
quick presentation before i continue.
im fabrizio, a 22 year old guy form italy.
since i stumbled on your site i was first of all extremely amazed and immediatly started using it and learned a lot of techniques from it.
recently i started developing a huge interest in trying to recreate your solver (i am a university drop out where i studied programming, new thing for me, which i failed miserably) but on thinking on how to recreate it, and let me specify, for personal pleasure in programming something that are not just useless lines of codes, i am encountering a lot of difficulties.
now the questions i had were. did you find help programming this on the internet or its just your personal experience? if the last one is correct, do you have any tips to help me on my quest?
one last thing, if you dont want to share anything because it would be a trademark problem or something similar i completly understand and im sorry for wasting your time.
thanks for the attention

Andrew Stuart writes:
Good questions. I have designed the site with programmers in mind – partly because some of the harder strategies are not at all easy for pen/paper solvers but are valid and interesting. But also because a lot of people like the challenge of solving puzzles logically in code. I intend that my docs should give enough information to work out how to make the algorithm. However since coding is the fun part I don’t post code. (really you just need the examples and the pattern stated clearly enough). My way is not the only way. Other people have other interesting/better ways. It is also not a race, so we’re not, as a world, trying to make the most optimal solution. But I do share bench-mark times using stock lists.

There is some code, the brute-force algorithm, for example, but that is because it is not original to me. Also, the packed-string code needs to be shared to be useful, and the front-end is readable javascript.

My biggest tip is to start simple. Don’t try and do everything. Second tip – I found it very useful to think about variants like Jigsaw and Sudoku X. These force you to generalise and be more abstract.

Monday 5-May-2025

... by: Bellmac, USA

Not sure if this is new. I used to manually enter puzzles, but have not been doing so for awhile. Today, when I started entering a puzzle manually, I noticed that when I entered a number it did not automatically advance to the next cell. It makes a bit more awkward with the change.

Andrew Stuart writes:
Tick "Auto Tab". I've noticed that peoples browser are dropping their settings for these tick boxes. Bit annoying

Monday 5-May-2025

... by: romboc, romboc@shaw.ca

How to turn off the "Hints Off" option? The latest KenKen solver version has this button enabled in the off version, and I cannot figure out any way to turn the hints back on.

Andrew Stuart writes:
So it’s a pulldown list. Click on it?
Off is the normal condition where all information is provided. The strategy, the pattern and the eliminations.

Friday 2-May-2025

... by: Hans Meine, Northern Germany

I just got the following clue:

Simple Colouring
(RULE 2): Two 7s in a single unit (in Box 1) have the same color in cells B3 C2 - all yellow coloured candidates can be removed

But the two colors used for the A/B coloring are purple and green. So the text should read "green" instead of "yellow".

Awesome tool, however, congratulations!

Best, Hans

Andrew Stuart writes:
You are not the first to point this out so I really should fix it!
I think it was recent when I changed the order of what gets drawn first but I cant remember why.
Version 2.34.2 should now display the yellow eliminated candidates
Hope I haven't created a knock on bug

Wednesday 30-Apr-2025

... by: Angi, Germany

I can’t clear the pop up and can not use the Buttons.

Andrew Stuart writes:
Yes it's been a horrible few days. I've now removed the ad from the Sudoku solver.
Playwire are not investigating unless I provide an example myself so I have to sit and wait for one I did that yesterday and they removed a rogue advertiser but it's clearly more widespread. I do want to have a bare minimum and not clutter the place. No ads should be going out of their boundary
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2015 2014 2013 2012 2011 2010 2009 2008 2007 2006
Thank-you everyone for all your questions and contributions.