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My game against the interactive diagram. I played White and won.

1. f5 Nh7 2. Nh4 Ng5 3. e4 Cf7 4. Nc4 Rag10 5. g4 Nc7 6. Bf4 h6 7. Ng6 Nce6 8. Nge5 Nxf4 9. Cxf4 Ch8 10. h4 Nf7 11. Nxf7 gxf7 12. Cxh6 Rg7 13. Rjg1 Rg8 14. g5 Cg7 15. Cxg7 Rxg7 16. f6 Rg6 17. d4 Rjg10 18. e5 R6g8 19. Bf5 d7 20. Rg3 e6 21. fxe7 Bxe7 22. Rf1 Rg7 23. Nb6 Bxa3 24. Nxa8 Be7 25. Rgg1 R10g8 26. Ra1 Qe8 27. Nc7 Qd8 28. Ra9 Ke10 29. Rxf9 Kxf9 30. Nd5 Ba3 31. Qa2 Be7 32. Qa9 Kg10 33. Ra1 Rg9 34. Qa10 Kf9 35. Ra9 Ke8 36. Qc10 Rd9 37. Qe10 Re9 38. Rxe9 Qxe9 39. Qxc8 Bd8 40. Bxd7

Is there any way to replay past games with the interactive diagram?

I am not sure what you mean by that. You want to be able to paste the game back into the diagram, and then step through it with the navigation button? Currently you can only step through the game you are currently playing (even after it ended), and the memory of it is erased as soon as you start a new one. I suppose I could add some text entry in the AI bar where one could paste a game so that the JavaScript can see it. I am not sure whether it is possible to attach a handler for Ctrl-V to the page as a whole, to trigger importing it from the clipboard. In any case I would have to add a SAN parser, but that should not be too difficult.

I am not sure what you mean by that. You want to be able to paste the game back into the diagram, and then step through it with the navigation button?

I wasn't thinking of that, as such, though it's not a bad idea. I was thinking of including a game in the HTML used to define a diagram. This could be useful for showcasing past games.

I see. That is currently not possible either. It is so much like the thing I mentioned first, that it would probably be easiest to combine such features: by default have some way to paste games into the diagram, but allow a way for the diagram description to define an initial value for that input element.

I don't seem to be able to find HG's piece values for this game. Can someone help?

I am not sure what exactly you are referring to. I never measured piece values explicitly for Grand Chess; I always assumed they would be equal to those of Capablanca Chess, as extra ranks behind the armies should not have much effect on game play. For Capablanca Chess the values are Q=950, C=900, A=875, R=500, B=350, B-pair bonus=50, N=300, P=100. There is a rather strong manifestation of the 'leveling effect', though: the super-pieces are effectively worth less when they face many lighter pieces. So sacrifycing one super-piece for R + minor or 3 minors ups the effective value of your remaining super-pieces compared to those of the opponent, which can give more than a Pawn in compensation (if you still have these super-pieces).

Ok, It is Capablanca which I remember then. Thanks!

You can add Pychess (https://www.pychess.org) to the list of places to play both people and AI. We have regular scheduled tournaments (including in Grand Chess) as well as a top of the line AI in Fairy Stockfish (although note that the top strength is still diluted to make processing efficient)

@Daniel Lee

Hello! Is there a way for someone to add new games to that website?

M. Badii - J. Stranjakovitch, Paris 1989 reached the position in the diagram below after

1.e4 a6 2.d4 b5 3.f4 Bb7 4.Bd3 f5 5.exf5 Bxg2 6.Qh5+ g6 7.fxg6 Bg7 8.gxh7+ Kf8

The game continued 9.hxg8=Q+ Kxg8 10.Qe2 Bxh1 with a win by White after 24 moves.

I see no reason for rules that may prevent early pawn promotions in Grand Chess. Most of us want games that are more interesting, not less. And after all, there is no limit to the number of promoted pawns on the board in Shatranj.

[EDIT] I should have specified the rules that I was objecting to:

"5. A Pawn can promote only to a friendly piece that has been captured, and for which it is exchanged."

"6. If no friendly piece has been captured, then a Pawn may not move beyond the 9th rank."

@ David

Pawn promotions before reaching the last rank can look more or less aesthetic depending on which games a person has played. I've seen comments elsewhere by chess players that they wish the board edge was 'made use of' (as though by chess 'tradition') in Grand Chess, by having promotions only there. However, anyone who's played shogi will note that in that classic game, earlier promotions than on the board edge are allowed by tradition also (the tradition evidently being that the first three ranks of an opponent are where his pieces or pawns start from in the setup, as is the case for Grand Chess).

I suppose that David uses the term 'early promotions' not so much to refer to promotions before the last rank is reached, but to promotion so early in the game that nothing has been captured yet. And I agree that this rule doesn't really make a more interesting game, but seems purely conceived for the convenience of playing it with woodware, without the need for extra pieces. (Which seems a bit strange, as it would still need two extra Pawns and pieces per player, presumably from a second orthodox set, which would leave plenty of spare pieces available for promotion.

On the other hand, one could argue that it is a nice tactical dilemma that when you are planning a promotion you should also take care something worthwhile is traded by the time you reach last rank. This happens so rarely, however, that it doesn't seem worth to complicate the rules for making it possible.

Note that although the orthodox game shown by David does have an early promotion, but not one where the promoted Pawn survives.

I think the rule you can only promote to a captured piece is good actually. There are some pretty powerful pieces in this game and this rule prevents an 'overpowering' of the game.

Also, I would say it would be fairly rare to find a pawn promoting before a capture of a piece.

H.G. says 'On the other hand, one could argue that it is a nice tactical dilemma that when you are planning a promotion you should also take care something worthwhile is traded by the time you reach last rank.'

I agree, and it also can lead to interesting play because you could sacrifice a piece knowing that you have a pawn to promote after. Fun times!

I can add that, except in the late end-game, it is extremely rare you would be allowed to promote and survive. The opponent will almost always sacrifice a minor to prevent promotion or capture the resulting piece on the promotion square. So it doesn't matter very much what is available as promotion choice; you will gain a minor for a Pawn when you can force a Pawn into the promotion zone. So you don't suffer very much if a minor is the only piece available as promotion choice. It is just that the opponent gets the choice not to trade his minor for it.

So the promote-to-lost-only rule doesn't affect the game that much. The most notable effect is that in a late end-game where there still is a super-piece and an unobstructed promotion is possible, you will have to pick a different super-piece. But since there are three nearly equivalent super-pieces, each giving an advantage so large that the game ceases to be a serious contest, that doesn't make much difference.

Hi Christine! I strongly resent Grand Chess forbidding any position with "extra pieces" on the board - one example being eleven pieces on one side (not counting pawns). These rules make me feel like I am playing chess with Damocles and we are both sitting with swords suspended over our heads. I am not comforted by any statistics proving that a sword almost never falls - just get me another chair!

Searching ChessBase 2000 for some standard chess games with nine pieces on one side produced: Stefan Fazekas - Norman Littlewood, BCF Championship 1963. The first capture (a pawn) was on move 23. A White Pawn captured a Black Rook on move 26 and promoted to a Queen. Black quickly won the game after White played 28. Rh1 - all three Queens staying on the board until the end. Worth noting: Stockfish calculates 28. fxg4, leading to a White victory.

1. Nf3 g6 2. c4 Bg7 3. Nc3 d6 4. d4 Bg4 5. e3 e5 6. Be2 Nc6 7. O-O Nge7 8. d5 Nb8 9. h3 Bd7 10. b4 O-O 11. Rb1 f5 12. c5 Bf6 13. Nd2 g5 14. e4 Be8 15. Nc4 a6 16. cxd6 cxd6 17. Be3 b5 18. Na5 Kh8 19. f3 Rg8 20. Rc1 f4 21. Bf2 Ng6 22. a4 Bd7 23. axb5 Qf8 24. b6 Qh6 25. b7 Bxh3

26. bxa8=Q Bxg2 27. Kxg2 g4 28. Rh1 gxf3+ 29. Kxf3 Nh4+ 30. Bxh4 Bxh4 31. Rxh4 Qxh4 32. Qg1 Qh3+ 0-1

I think that promotion rule is the greatest promotion rule of all time lol. That sword you speak of doesn't worry me, that sword is always over my head anyways, if I'm playing a game or not too hehe.

@Christine,

I prefer the gross chess promotion rule where you have plenty of pieces to promote to.