Keywords: Problem, Software

[ext] is a website with a collection of more than 9000 (and increasing) user contributed Go problems of various types, whose difficulty ranges from 30k to 6d+. These problems can be browsed in various ways, solved interactively, and discussed in quite a few [ext] languages.

Credibility: The problems and solutions are created by amateurs of varying levels, which may leave place for improvement. (This does happen with community feedback, but takes time as it's up to the author or the moderators to actually implement corrections.)

Note: Not knowing where to put it, I'll just temporarily put it here: Adum [ext] decided to include in the problem [ext] addition page that "...By adding and editing problems you grant the right for goproblems to use and redistribute these problems...Such distributions may be commercial. ". It doesn't change I guess what the site means to most of us, but contributors of original problems and sets such as the wonderful 4x4 by ferdi should be aware. (Please update this and move to the appropriate place)

Table of contents

[1] Problem Types

All of the problems in the site belong to one (and only one) of these:

  • Elementary was intended to be problem for absolute beginners, such as placing a stone in the middle of three spaces to kill. It is however used for less basic problem, with basic principles which are hard to place elsewhere.
  • Life and Death is just that. Kill or Live depending on whose move it is.
    However do notice that quite a few authors consider ko or even seki as wrong where it is possible to avoid and some even consider only the best ko as a correct solution (though it's more common to place such requirements in best move problems or to warn first).
  • Best Move requires you to play the best possible sequence you can in a given situation.
  • Joseki is a little problematic since most authors around aren't strong enough for joseki/fuseki problems, so take these with a pinch of salt.
  • Fuseki is a little problematic since most authors around aren't strong enough for joseki/fuseki problems, so take these with a pinch of salt.
  • Tesuji
  • Endgame: When given a part of the board, unless said otherwise make no assumptions about the rest of it. May involve counting points/ ko threats.

They are further categorized by Difficulty and Groups (collection/ type of tesuji/ cut-connect...)

1.2 Difficulty

Difficulty is hard to get right. Problems difficulty is automatically set according to the pracentage of pro users who fail to solve it correctly on their first attempt. It's described as (58) 7 kyu / 11 secs (1307)

  • 58 is the percentage of registered people who failed to solve it on the first attempt (7 kyu is based on it)
  • 11 secs is the average time it took those who succeeded.
  • 1307 is a new elo like system based on the rating of the solvers
 difficulty:  ------Easy------ ------------Medium ---------- ------------------Hard------------------
       rank:  30k 25k 20k 18k | 15k 12k 10k  8k  7k  6k  5k |  4k  3k  2k  1k  1d  2d  3d  4d  5d 6d+
       fail:   0% 20% 25% 30% | 35% 40% 45% 50% 55% 60% 64% | 68% 72% 76% 79% 82% 85% 88% 91% 93% 96%

1.3 Groups

The [ext] groups allows browsing problems by

  • [ext] Style (such as "Counting Points"/"Shinogi"/"Corner Boxes" etc)
  • [ext] Collection (such as "GuanZiPu"/"L Group"/"Corner Based" etc)
  • [ext] Sequence (such as "An audacious attempt for victory by Gennan Inoue Inseki"
  • [ext] Tesuji (such as "Under the Stones (secret)"/"Snapback (secret)"/"Oiotoshi" etc)
    many of which are marked secret as seeing the type would be a big hint while solving the problem and therefore these groups are inaccessible otherwise!
  • [ext] Joseki (such as "Joseki followup"/"3-4 (komoku) Joseki" etc)

[2] Finding Problems


The [ext] main page lists the eight latest added problems, provides a random problem (selecting a type and approximate difficulty) and the time trial.

Time Trial

Starting with four lives at the level on which you decide upon entering it from the main page, you advance when correctly solving a problem under 60 seconds, losing a life otherwise. Every certain amount of problem you get an extra life. The trial doesn't end (though this is unconfirmed as I've never survived it at 6d :) but you do progress between levels. Registered Users have a list of their trials accessible from their user page. (Problems from the strange and fun categories aren't included.)

2.1 Problems Page

The [ext] problems (link at the top) page offers links to the groups page, pattern search page and flagged problems page[41] and the ability to

  • select better refined random problems (such as un/solved/attempted etc.)
  • see recent discussion on problems (comment search)
  • look up text in problems

2.2 Pattern Search

[ext] Patten Search allows you to look up specific situations, but be careful to enter only the relevant stones and the surrounding position may vary.

[3] Solving and Study

There are a few ways to use the site. The default is the java applet. Other options are the ]|#toc14] and eidogo.

Once you've decided you know the solution, play it out. After you do you can use the show solution menu in the applet, which has several options:

  • numbered solution which shows the final diagram of the first correct branch in the tree
  • Animate Solution which shows the same variation as the numbered solution but taking a second between moves
  • Navigate Solution which allows you to browse the tree and see the different moves and responses covered by the author.

Navigate Solution is a good way to explore the reasons behind the solution. Together with the ability to add comments and ask questions, this is a great tool for improvement.

It's also possible to use See Attempt Paths[42] to see what others did.

It is also recommended that you go back to the beginning and imagine the variations after you're done with the problem, to improve your reading.

[4] Discussion and Feedback

Problem Specific

  • Comments
    Due to spam problems, only registered users can comment on problems.
    The new applet allows you to comment from within the applet on any location in the tree.
    (Note that comments may be disabled but not deleted.)
    There are four types of comments:
    (It is still possible to access the old plain html comment pages eg [ext] problem 5 comments
    but it's not clear where in the tree the comments were placed, using the new applet)
    • Right and Wrong used to suggest what you believe should be a correct or a false variation respectively.
    • Question
    • Comment
  • 4.1Flags
    There are four types of flags. (This feature requires JavaScript)
    The flagged problems are then concentrated on a single page to point the moderators to the problematic stuff.
    Both Duplicate and Needs Fixing should be used together with the comment system, adding the reason of the flag.
    • Good Problem: this problem is well-constructed
    • Needs Fixing: this problem has some invalid paths
    • Duplicate: this problem already exists on the site
    • Invalid: this problem is just totally, unfixably wrong
  • Preference
    • Coolness: You can give the problems you solve a rating between 1 and 10 according to their appeal to you (Coolness Menu in the applet).
    • Favorite Problems: Registered users may add problems to their favorites list, accessible from their user page (and public).
  • 4.2See Attempt Paths
    is a tool which shows the variations which registered users took (there's also a nick-var list however only of those who allowed it in their profile) which of course is extremely helpful for the author in seeing which variations may need extra attention.


The new [ext] forum, the link to which can be found at the top of any page, has integrated user accounts, which means that registering in the main site is enough to be able to use it.

The forum has four sections: News for site news; Suggestions to suggest site improvements; Help for help mostly related to site issues but not restricted to it; General for general discussion.
(The old [ext] zorum is still accessible but isn't used anymore)

If it wasn't clear enough--There's nothing stopping you from using the forum for anything, but normally senseis or godiscussions is what's used for site-unrelated issues.

[5] Adding problems

First of all, why? Besides this helping the community, it also helps you improve.
The reading it takes to cover a position in a way required to make a problem is something most people normally don't do. It also helps you understand what makes the position work the way it does. Also consider making variations--What will be of a problem if you change a stone here, or take a liberty there? Have fun... ;)

The Add Problem link at the top allows you to add a problem.
Registered users have a link back to their page, a list of their problems and the ability to edit them later.
Problems can be either premade or made online using the graphical applet. The later is more common as you can enjoy both the ease of marking with RIGHT/ CHOICE etc tags which otherwise you would have to add manually and the isomorphism.

5.1;Isomorphism: Joy and Curse - The new applet auto links similar positions to which you get by different paths, which allows for a great ease in both the making of problems, their later editing and even their navigation. However neither does the old applet support this (making the downloadable version problematic to use) nor do any other editors (making the collection less useful).

It is recommended that you check first using Pattern Search to avoid the wasted work of adding a problem which already exists.

It is also important to note that though single positions may not be copyrightable (see discussion elsewhere), problem solutions (as in collections of variations) and problem collections are in quite a few countries. Even if they aren't where you're located it'd be extremely rude to do so to your fellow problem authors.

Be prepared for corrections. It might be a good idea to use gotools for simple problems to improve coverage at first. Also try to add at least a single refutation for any opponent move for the problems navigation. Do not place comments on the computers moves as they'll just flash by.

It might be a good idea to read the graphical editor's help, it covers all the key tools well.

[6] Compatibility and the Old. site

It is still possible to use the [ext] if the new applet fails you or if you're having problems with the new comment on branch/ isomorphism[51] (downloaded version of the site also uses it) but be aware:

  • the old comment system won't show you where in the problem the comment was placed;
  • the Discuss link at the top is to the old [ext] zorum which is neither linked to the new user system nor is used anymore for discussion remains (strictly as an archive).

Also note that it's possible to use Eidogo as was mentioned in [2] however there's no immediate way to see comments nor is isomorphism supported there either.

Mobile Phones currently aren't supported, however it is possible to view the rss problem feed with opera on almost any recent phone, which gives you some recent problem. It is also possible to access specific problems using the [ext] util/img.php link, setting the sz beyond 128 is also possible.

[7] User Accounts

Why register? Registration is free and allows you to comment both on problems and in the forum. As well as have a list of your recent comments and problems, your favorite problems list which would be publicly available from your public page which your problems which you'll be able to edit would link back to in addition to the ability to set the preferred interface language and your problem solving attempts would be kept for a week at a time (deleted every Sunday).

Pro Account
Due to heavy DB usage created by keeping solving attempts, adum decided to limit it to the pro users only. These accounts keep they attempt paths and are able to download an offline version[8]... (They are free to translators, moderators and contributors of 30+ problems)

[8] User Written Tools

TODO: Bring this section up to date.

  • [ sorter|] - server not found
  • - sort problems corresponding with the DI- and GE-identifier; Linux sh script
  • - sort problems into directories corresponding to the DI-identifier
  • Sort Problems By Rank - the same as, but for Windows-users
  • GoGrinder/ - sort .sgf and corresponding .dat files from GoGrinder's stats/ directory; Linux bash script, can also be used in Cygwin (Windows) last edited by Dieter on July 31, 2014 - 12:48
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