Snyder notation

[Greggold]

When introducing the app in youtube, I suggest the Snyder notation be identified as such. I only discovered Sudoko-web-app yesterday, and it is fabulous. I first learned of Snyder notation from the Cryptic website, but I have been frustrated by the lack of a good app that allows its use. I have found several previous apps but none come near Sudoko-web-app. If you promote Sudoko-web-app as a Snyder-enabled app, I believe more people will find it. Snyder notation allowed me to advance from easy puzzles to the most difficult levels in a very short time. Until now I preferred the Web Sudoko app, that allows Snyder notation by the trick of using a full stop, with the Snyder digits before and pencil marks after - it works but it is a bit clunky.

When Snyder notation is mentioned, its worth making a simple clear statement to define it, for example something like in a 3x3 block when a candidate only occurs in 2 cells, and compare this to the meaning of usual pencil marks which are about candidates occurring in a particular cell. Maybe mention the distinction of Snyder pairs that are in line as opposed to in diagonal cells.

At the risk of repeating myself, Sudoko-web-app is way better than competing apps!

[grantm]

Thanks for your feedback. I intend to record a new intro video to cover the features added since I did the original. I'll definitely bear your feedback in mind.

[Greggold]

The use of Snyder notation as a solving strategy transforms an average player's ability. It renders obsolete most items in the long list of techniques listed on websites such as Hodoko (http://hodoku.sourceforge.net/en/tech_intro.php), that include X-wings and swordfish, to the extent I once hoped that all that I need is a degree of competence with Snyder notation. Basic techniques such as naked pairs, hidden pairs and X-wings are still necessary, however with the sudokoexchange.com app these are made much easier to pick with the shading that shows all instances of a candidate.

I have learned that the occasional extreme-level puzzle resists solution with Snyder notation technique (example www.websudoko.com puzzle number 18726116888, as provided in this link:
https://sudokuexchange.com/play/?s=AD54kv2QbTi3ws8jLdR8vf13CR&v=sbe ). I estimate puzzles that resist solution in this way comprise less than 10% of extreme puzzles.

When such a puzzle is encountered, I find that techniques listed in Hodoko such as unique rectangle (6 types plus variants), XYwing, skyscraper and others sometimes succeed. However these can be very time-consuming to apply. I am satisfied that these three just mentioned do not work in the above puzzle.

What are the best options in such a circumstance? How can I develop a shortlist of techniques? Is there a method sudoko authors use to design a puzzle to resist Synder technique, and can a clue to a solution be inferred from this?

[grantm]

The puzzles on the websudoku.com site have a reputation for not being especially difficult. On the SudokuExchange.com site the most difficult category is labelled "Diabolical" and I think most people would struggle to solve any puzzles in this category using only Snyder notation. But if you get stuck the hint button will tell you the easiest technique that would move you forward.

[Greggold]

May I make 2 comments on the hint button/function in Sudoko exchange. This help is outstanding and has led me to learn skyscrapers, strong links, XYZ-wings, some unique rectangles and swordfish, while other techniques (WXYZ-wings etc) remain so far in the too hard basket. I now prefer puzzles such as the Brainsword evil category, and in about 10% of cases solve them with no hints. Doing hard puzzles with the hint backup is a good way to learn.

1. With a 2 strong links, the comment is always made "the 2 strong lnks are therefore joined with a weak link" even when this is not true, as shown in the attached screenshot (2_Str_lk4.png) of the help (I hope the png file is readable, I attached it twice). It is important that the statement clearly allows the user to rule in or rule out a strong link, and this time its misleading, as in fact the 2 strong links are joined by a strong link.

2. With complicated techniques such as WXYZ-wings, the complexity makes them difficult to identify. Once they are pointed out, I can see them, but what I lack is a quick strategy or tests to find them, or to rule them out.