Solver App for Android
Strategies for Popular Number Puzzles
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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!

Sunday 17-Sep-2006

... by: Lukas, Germany

Bowman Bingo doesn't work any more in the new version:

No strategy request exists for this number: 35

Andrew Stuart writes:

Thanks, caught the bug now. Fixed.

Friday 15-Sep-2006

... by: Jeff Loeb, United States

I do not see the Take Step and << buttons on this Scanraid solver. I see both buttons on the Sudoku Assistant/Solver available at

Also, when I ask to receive the PC version of the Scanraid solver, what I get instead is an "ad" for the Sudokulist game.

Andrew Stuart writes:

Hi Jeff, the buttons are above the strategy list on the right hand side?

I'm was part of the team that made the Sudokulist. I'm working on a replacement which will be similar to this web page solver but sophisticated, less glossy. Anyone who purchases the sudokulist will be entitled to a free upgrade, so it don't matter which version you buy. The Current Sudokulits version is mainly meant to provide a nice set of games. The solver is a little primitive now, one year on.

Thursday 14-Sep-2006

... by: susan, usa

I used to be able to put in my sudoku puzzles hit "take step" and then go back one to have all numbers in each empty box so I could do even the first step on my own. Now it will not go all the way back to that first step? Is there another way I can get it to that point? Thanks!

Andrew Stuart writes:

Hi Susan,
Yes if you want to see all the candidates in every cell, just use the save button and the reload. Printable version from there.

Sunday 10-Sep-2006

... by: Van Williams, USA

There's no link to an explanation to Bowmans Bingo.

Andrew Stuart writes:

Seemed to work for me. I'm working on more docs so I don't have to refer to external links which don't do a great job of explaining strategies sometimes

Sunday 10-Sep-2006

... by: Sander Huisman, Netherlands

I would like to know why empty rectangle is categorized as an uniqueness-solving technique ?
Best Regards,
Sander Huisman

Andrew Stuart writes:

My mistake. Changed that now, don't know what I was thinking at the time! ;=)

Friday 8-Sep-2006

... by: Larry, USA

I've been using your (awesome) solver to try and learn how to do Sudoku's better, and noticed one thing which I think may be a very minor bug. I had turned off some of the strategies so I could see the solver use other strategies to solve the puzzle. But even though I had the X-Wing stragegy turned off, it still looked like the solver was using it when trying to solve the puzzle (I'm using Firefox 1.5). That's it. Thanks again for a great tool (I was amazed at the things you were doing in javascript in the previous version)

Andrew Stuart writes:

Hi Larry, some easier to spot strategies like X-Wings are sub-sets of some of the more complex ones and they may use the same candidate formations. Infact X-Wings can be expressed in the logic of five or six of the higher ones. Its seperated out since its easy to spot in its own right and was discovered before the other ones. The results box will name the strategy used - so check that.

I reached the limit on what I could do in javascript for the higher strategies - purely a limitation with the language and its speed (its interpreted, not compiled).
OK, found the bug with the X-Wing checkbox. Fixed. Thanks!

Thursday 7-Sep-2006

... by: Frank, California

Thank you for the wonderful website! I have looked at sododu books with various graphics and explanations, and not made much progress. With your website I especially like being able to choose puzzles containing specific problems and approaches. Being able to take-a-step through the approaches, and being able to step back is very useful. I have been going through the example puzzles more than once to see if I can begin to utilize the more difficult techniques. I am a relative beginner. I have done about 30 easy puzzles, and 30 medium puzzles. I am trying to understand how to correctly use hidden triplets/quads. I am still not quite sure why in a particular column certain triplets are drawn out to use when it seems that in some puzzles there are 2 or more triplets. Is the deciding factor that there must be two boxes with only those numbers?
I have tried to use the: Candidates can be O Edited function. I tried to delete candidates, but when I press delete or return the entire window disappears. I am using a MiniMac 1.5 GHz G4 using OS 10.4.7. I have tried to edit on the large and small puzzle. What buttons should I press?
Thank You!

Andrew Stuart writes:

Hi Frank, on vacation at the moment so I'm only answering 'easy' questions. We might need a bit of emailing to and fro to get to the bottom of these. I'll be back next week. Contact you then

Thursday 7-Sep-2006

... by: Sandpiper45, Saskatchewan, Canada

Your on-line Soduko Helper is awesome and I really prefer it to the version you sell for download. The added feature of editing the small numbers is the key. Is it possible to update your download version to include that, if not the whole on-line solver?
Keep up the great work. Great challenges and lots of fun!

Andrew Stuart writes:

Hi Sandpiper45, thanks for the feedback. I'm working on a completely new version of the Sudokulist which will have everything in this solver plus a bit more. Storing all user requests and suggestions for incorporation. This will be free for existing purchasers of the program.

Wednesday 6-Sep-2006

... by: Ben VT, USA

Load Sudoku:

Do you have a good link how to explain X-cycles? I have a bunch of puzzles that I can only solve with the X-cycles option (or something much much harder that I do not understand)

Monday 4-Sep-2006

... by: Paul Akehurst de Visme, Portugal

Not clear on the function of the 'Save' Button. I had hoped that it would save to a file somewhere the current board, as entered by me. I get the pop-up 'Current board saved' but can it be resurrected at a later date, and if so where is it kept?

Andrew Stuart writes:

Save only works if you don't navigate away from the page. It's really only useful for reloading at a certain point, like the start. I would like to make it a proper save but I've not fully explored cookies via javascript yet and don't want to create a security issue with the browser. High on the list of items to improve, however.
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Thank-you everyone for all your questions and contributions.