Hi, I think allowing null moves would be a good thing. Sometimes null moves (and the variations they spawn) can illustrate what the idea behind a move is and it's the easiest way to show what is being threatened.
One possible way of playing a null move could be to play a king on top of the other and then the null move could be entered. That's how hiarcs chess explorer does it.
Hmm yes. A problem is that it's not a legal move, and doesn't produce valid PGN.
I guess that's why the null move is basically non-existent on chess servers even in analysis type situations.
Thinking over it, I can just say, "refer to chapter X to see what would happen if black were to move again." And start the FEN with the side that just moved to move.
And thank you for the fantastic study platform!
Many programs accept "--" as a move in a PGN file to denote a null move. But it's not standard, no (has the standard been updated since 1994?)
Null move is useful for analysis especially when using an engine. They are usually found in a variation to show the threat of opponent.
I knew two commercial GUI's which supported this, HCE (mentioned by Squarology) and Fritz by chessbase.
The free GUI's winboard/xboard and "scid vs PC" also supported this.
The notation is -- or double dash.
[Event "?"]
[Site "?"]
[Date "?"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
1.e4 e5 2.Nf3 ( 2.-- Nc6 3.Nf3 ) 2...Nc6 *
pourquoi il ni a pas de coup ilégo
But of course the problem of implementing it is more complex than adding it to the PGN as a possible move.
Suddenly there is a move that is only legal to enter in analysis mode, not during games. Even in analysis mode it doesn't count as a legal move for things like stalemate.
But it would be nice to have it working, especially combined with engine analysis. GM Axel Smith's "Pump Up Your Rating" talks a lot about hitting 'x' in Chessbase, which apparently lets an engine think about the position after a null move, and using it as a tool for finding threats. When you see a move in an engine line that you don't understand, replace it by a null move and you probably find out what the strange move was preventing, that sort of thing.
