Answers.Body: <p><strong>Threats</strong>
  The elegant notion of threat (which is essentially what is asked about) is central to the world of adversarial chess problems (direct mates &amp; self mates).</p>
  <p>Roughly speaking, suppose White (who I will take to be the active player in what follows) has a winning move (call it a <strong>key</strong>). Then we imagine what could happen if White were to get a second move right away (or equivalently, if Black were to play a totally irrelevant move). A move that continues to win is called a <strong>threat</strong>. A Black move is called a <strong>defence</strong> if it defeats the looming threat. Of course now there will be a different winning continuation for White! (Indeed there must since by hypothesis the key wins for White.) A key may have multiple threats.</p>
  <p>Focusing on threats &amp; defences, massively reduces the branching factor, and can render the solution more comprehensible. The concept of threat is also crucial for thematic settings and consequent artistic appreciation.</p>
  <p>Threats are not always applicable:</p>
  <ol>
  <li><strong>Check</strong> If the key is checking, then an immediate Black response is
  <strong>entailed</strong> (to use the terminology of combinatorial game theory).</li>
  <li><strong>Block problem</strong> There are many positions where White has no win in time after the key unless Black actually moves. (aka &quot;Zugzwang&quot;.) These are very interesting, and a lot of endgame theory depends upon them. In some, even an infinite number of White moves will not suffice to dislodge Black if he is never required to move. For example, <a href="https://www.chessjournal.com/chess-trebuchet/" rel="nofollow noreferrer">trebuchet</a>.</li>
  <li><strong>Unrealizable</strong> If <em>all</em> Black moves defeat the threat, then it's a waste of time &amp; confusing to explore the hypothetical. Miniatures can often fall into this category. In this case if solving e.g. with Popeye it's best to disable &quot;threats&quot;. [It might be best to have this to automatically decided per each individual White move, rather than a global option.]</li>
  </ol>
  <p>But most often, the notion of threat gives a massively simpler perspective of the game-tree.</p>
  <p>I’ve wondered if a similar concept could be used in interpreting tablebases for endgame studies, because they can otherwise be opaque. It may also help with regular chess engines.</p>
  <p><strong>Diminishing value of chains of threats</strong> In algorithmic terms, threats can be cascaded recursively into a chain (move A threatens B threatens C etc) in problem engines.</p>
  <p>However, while knowing a single &quot;threat&quot; move and its defences simplifies the picture of a position, a <strong>chain</strong> of threats will usually diverge rapidly from the correct value of the position.</p>
  <p>If White can play an indefinite number of moves, it will teach a player how to move pieces, and how to mate. It's a bit like a tutorial prologue at the beginning of a large video game to show how the commands work. But it is very limited in scope, because the nature of chess is adversarial.</p>
  <p>The mathematician Claude Shannon famously remarked that if null move is legal, then by a simple strategy-stealing argument, chess cannot be a win for Black.</p>
  <p><strong>Seriesmovers</strong>
  There are certainly problems where only one side moves: so-called seriesmovers. These may be very interesting, but they teach us little about the regular game.</p>
  <p>A variant of the seriesmover, the so-called &quot;parry series&quot;, allows e.g. White to make all of the moves, except that Black can respond to checks. (Normally in seriesmovers, checking moves are not allowed except for the final move.)</p>
  <p><strong>Lichess.org</strong>
  Apart from Apronus, one can also do a null-move exercise with lichess.org. Just play White moves in the board editor and when one puts the opponent in check, go to analysis engine (ensuring that Black is to play) and accept the Black move.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-08-28T06:43:43.907Z
Answers.Text: @user30536 which lexicon is this please?
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-08-28T07:45:07.920Z
Answers.Text: "The current chess problem lexicon" for me is Milan's Encyclopedia - there can only be one ;-) Quote: "A problem in which White has to threaten something (specific) to make Black weaken his position, in order to mate in the stipulated number of moves. Mere waiting would help Black delay the outcome." But a SCHWALBE article (?) proves @user30536 right - with things like threatening zugzwang or other shenanigans.
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-08-28T11:04:47.167Z
Answers.Text: I see there are lots of entry for threat in V&V. Basically "A move or variation which White will play (usually following his key) if Black does nothing to defend against it. Problems which do not have threats following the key are blocks. (Definition 
  from FIDE Album.)"
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-08-29T03:36:44.950Z
Answers.Text: I think V&V presume that "threat problem" = "problem with threats"
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
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Answers.LastEditDate: 2023-08-29T03:45:31.663Z
Answers.UserDisplayName: Laska
Body: <p>I am looking for interactive exercises that involve playing chess against computer which makes nullmoves allowing the learner to attack without thinking of defense. I know of one platform which allows this kind of exercises. For example:</p>
  <ul>
  <li><a href="https://www.apronus.com/chess/puzzle/?p=0rnbqkbnrXppppppppX8X8X8X8XPPPPPPPPXRNBQKBNR_w_KQkq_-_0_1&amp;N=0&amp;w=&amp;h=%3Ch3%3EWhite%20to%20play.%3C%2Fh3%3E%3Ch5%3EThe%20computer%20moves%20only%20when%20checked%20or%20threatened%20with%20mate%20in%201.%3C%2Fh5%3E&amp;m=33" rel="nofollow noreferrer">The computer moves only when checked or threatened with mate in 1.</a></li>
  <li><a href="https://www.apronus.com/chess/puzzle/?p=0rnbqkbnrXppppppppX8X8X8X8XPPPPPPPPXRNBQKBNR_w_KQkq_-_0_1&amp;N=0&amp;w=&amp;h=%3Ch3%3EWhite%20to%20play.%3C%2Fh3%3E%3Ch5%3EThe%20computer%20moves%20only%20when%20its%20eval%20is%20below%20-3.%3C%2Fh5%3E&amp;m=33&amp;V=3000" rel="nofollow noreferrer">The computer moves only when its eval is below -3.</a></li>
  </ul>
  <p>This resource research is needed to write a master thesis focused on this kind of exercises. In this kind of work it is customary to include detailed information on already existing resources.</p>
  
Tags: <puzzles>
Title: Examples of interactive exercises to play chess with nullmoves
ThreadText: # Examples of interactive exercises to play chess with nullmoves
  
  (Asked by: username_0 on 2023-08-24)
  
  I am looking for interactive exercises that involve playing chess against computer which makes nullmoves allowing the learner to attack without thinking of defense. I know of one platform which allows this kind of exercises. For example:
  
  * [The computer moves only when checked or threatened with mate in 1.](https://www.apronus.com/chess/puzzle/?p=0rnbqkbnrXppppppppX8X8X8X8XPPPPPPPPXRNBQKBNR_w_KQkq_-_0_1&N=0&w=&h=%3Ch3%3EWhite%20to%20play.%3C%2Fh3%3E%3Ch5%3EThe%20computer%20moves%20only%20when%20checked%20or%20threatened%20with%20mate%20in%201.%3C%2Fh5%3E&m=33)
  * [The computer moves only when its eval is below -3.](https://www.apronus.com/chess/puzzle/?p=0rnbqkbnrXppppppppX8X8X8X8XPPPPPPPPXRNBQKBNR_w_KQkq_-_0_1&N=0&w=&h=%3Ch3%3EWhite%20to%20play.%3C%2Fh3%3E%3Ch5%3EThe%20computer%20moves%20only%20when%20its%20eval%20is%20below%20-3.%3C%2Fh5%3E&m=33&V=3000)
  
  This resource research is needed to write a master thesis focused on this kind of exercises. In this kind of work it is customary to include detailed information on already existing resources.
  
  **Tags:** puzzles
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2023-08-24. Score: 1
  
  **Threats**
  The elegant notion of threat (which is essentially what is asked about) is central to the world of adversarial chess problems (direct mates & self mates).
  
  Roughly speaking, suppose White (who I will take to be the active player in what follows) has a winning move (call it a **key**). Then we imagine what could happen if White were to get a second move right away (or equivalently, if Black were to play a totally irrelevant move). A move that continues to win is called a **threat**. A Black move is called a **defence** if it defeats the looming threat. Of course now there will be a different winning continuation for White! (Indeed there must since by hypothesis the key wins for White.) A key may have multiple threats.
  
  Focusing on threats & defences, massively reduces the branching factor, and can render the solution more comprehensible. The concept of threat is also crucial for thematic settings and consequent artistic appreciation.
  
  Threats are not always applicable:
  
  1. **Check** If the key is checking, then an immediate Black response is
     **entailed** (to use the terminology of combinatorial game theory).
  2. **Block problem** There are many positions where White has no win in time after the key unless Black actually moves. (aka "Zugzwang".) These are very interesting, and a lot of endgame theory depends upon them. In some, even an infinite number of White moves will not suffice to dislodge Black if he is never required to move. For example, [trebuchet](https://www.chessjournal.com/chess-trebuchet/).
  3. **Unrealizable** If *all* Black moves defeat the threat, then it's a waste of time & confusing to explore the hypothetical. Miniatures can often fall into this category. In this case if solving e.g. with Popeye it's best to disable "threats". [It might be best to have this to automatically decided per each individual White move, rather than a global option.]
  
  But most often, the notion of threat gives a massively simpler perspective of the game-tree.
  
  I’ve wondered if a similar concept could be used in interpreting tablebases for endgame studies, because they can otherwise be opaque. It may also help with regular chess engines.
  
  **Diminishing value of chains of threats** In algorithmic terms, threats can be cascaded recursively into a chain (move A threatens B threatens C etc) in problem engines.
  
  However, while knowing a single "threat" move and its defences simplifies the picture of a position, a **chain** of threats will usually diverge rapidly from the correct value of the position.
  
  If White can play an indefinite number of moves, it will teach a player how to move pieces, and how to mate. It's a bit like a tutorial prologue at the beginning of a large video game to show how the commands work. But it is very limited in scope, because the nature of chess is adversarial.
  
  The mathematician Claude Shannon famously remarked that if null move is legal, then by a simple strategy-stealing argument, chess cannot be a win for Black.
  
  **Seriesmovers**
  There are certainly problems where only one side moves: so-called seriesmovers. These may be very interesting, but they teach us little about the regular game.
  
  A variant of the seriesmover, the so-called "parry series", allows e.g. White to make all of the moves, except that Black can respond to checks. (Normally in seriesmovers, checking moves are not allowed except for the final move.)
  
  **Lichess.org**
  Apart from Apronus, one can also do a null-move exercise with lichess.org. Just play White moves in the board editor and when one puts the opponent in check, go to analysis engine (ensuring that Black is to play) and accept the Black move.
  
  > **Comments:**
  > **username_1**: @user30536 which lexicon is this please?  
  > **username_2**: "The current chess problem lexicon" for me is Milan's Encyclopedia - there can only be one ;-) Quote: "A problem in which White has to threaten something (specific) to make Black weaken his position, in order to mate in the stipulated number of moves. Mere waiting would help Black delay the outcome." But a SCHWALBE article (?) proves @user30536 right - with things like threatening zugzwang or other shenanigans.  
  > **username_1**: I see there are lots of entry for threat in V&V. Basically "A move or variation which White will play (usually following his key) if Black does nothing to defend against it. Problems which do not have threats following the key are blocks. (Definition  from FIDE Album.)"  
  > **username_1**: I think V&V presume that "threat problem" = "problem with threats"  
  
  ---
  
  