Looks like an interesting game, although I am not sure it qualifies as a chess variant. Could you explain the rules? They are not on a pubicly accessible website, in so far I could find.

[Edit] Oh, I found a description in a PDF file on Google Drive. Some things are not yet clear to me, though:

• It says the Pawn only moves one step. But is this only forward, or can it also move backward, when going to an empty square?
• It says the win is by taking or turning all enemy Castles. But Castles can also be destroyed by their owner, through splitting them up. Which is neither taking nor turning.) Is it illegal to split up your last Castle?
• What if I capture my opponent's last Castle by splitting up my own last Castle? Is this allowed? And if not, who would be at fault? Is it more forbidden to split up the last Castle, or more forbidden to move into its capture range?
• Does a promotion reset the 50-move counter?
• Does combining friendly pieces count as a turnover, for resetting the 50-move count?

I'm intrigued and it looks cool, but confused by the knight being a bishop + pawn.  I suppose so many things are breaking apart and coming back together that its value doesn't have to always match the sum of its parts.  Maybe the knights are used at opportunistic times only?  Shout out to Furgus Duniho for the very similar Fusion Chess, but I'll grant that this adds pawns into the mix (and I love how the openings play out), and I also like the visual simplicity of literally adding the rings together.

Indeed, the particular combinations of rings that you have at any moment is not really preserved for a long time, nor hard to improve when sub-optimal. Piece values only have meaning in more conventional chess games because you typically will be stuck with a piece for a very long time, possibly to the end of the game, and if you have a weaker piece there is not much you can do to trade it for something more valuable. Here the actual combination is more like a positional advantage. Temporarily having the Bishop lose its moves by combining it with a Pawn is similar to blocking a good diagonal for a Bishop with a Pawn in orthodox Chess. (The Bishop might keep some of its other moves in that case, but here the 'Pawn' will temporarily acquire Knight ability, which should provide even better compensation.)

Yet you probably would not strive for combining your own Bishops with a Pawn. But remember that you can also 'turnover' an enemy Bishop by merging it with your Pawn, and that would be extremely advantageous, as now it is the opponent that loses the Bishop, and won't get it back when you split them up again. It would in fact be pretty hard for him to get it back at all. So it is really the value of the individual rings that play the role of piece values here.

• Pawn moves ahead one square and take diagonal forward one square. Pawn turnover ahead one square.
• Yes, is illegal to split up your last Castle, but if you have the last castle in check and it can turnover a queen ahead to get free from check so you can do it.
• Good question. Capture the opponent's last Castle by splitting up your own last Castle is a illegal move, because the result is no castles on board.
• "Does a promotion reset the 50-move counter?" It works like it on traditional chess? I don't know, but seems interesting question, I vote to reset :)
• "Does combining friendly pieces count as a turnover, for resetting the 50-move count?" No. Combining friendly pieces is not turnover, because a turnover is a take possession, like turnover in american football.

[I'm intrigued and it looks cool, but confused by the knight being a bishop + pawn.  I suppose so many things are breaking apart and coming back together that its value doesn't have to always match the sum of its parts.  Maybe the knights are used at opportunistic times only?  Shout out to Furgus Duniho for the very similar Fusion Chess, but I'll grant that this adds pawns into the mix (and I love how the openings play out), and I also like the visual simplicity of literally adding the rings together.]

Turnover, like chess, goes beyond a simple game, it has esoteric symbolisms. Castle made by 3 pieces has the symbolism of number 3. Keep board with 8x8 squares has the symbolism of number 7 and tetraktis 4+3+2+1 etc. Bishop is the magical or spiritual piece of chess, and it moves like a cross to bring a lot of other symbolisms that confirms the esoteric value of chess. Bishop + Pawn = knight because it is a man (pawn) with power (spiritual power from bishop), so in medieval battle, knights is it, a man mounted in a horse is much more stronger.

If you play the game, you will realise its difference on tactics, because you are sharing pieces with opponent. It create a kind of statu quo between pieces and it is really interesting. New players of course will play trash matches, but good turnover players can make passionate matches, and I swear, is really almost impossible to draw in Turnover, because this game is very offensive. So, yes, is very dangerous create knights, because bishops are very useful and when you move a knight you let behind a bishop and the opponent can think a strategy to take your bishop.

About simplicity, the game uses only 3 pieces, a magical number and a strong algorithm to the way human mind works. So when you are playing the game, seems all possible moves from all pieces on board can be visualized in your mind and it is good, because your mind can dedicate more time to think what move instead of recognize pieces first to think what move after. And your mind stress less then in chess.

Play Turnover: 

Player vs computer: https://glukkazan.github.io/checkmate/turnover.htm

Player vs player: https://glukkazan.github.io/checkmate/turnover-board.htm

Player vs computer (PawnFreeToCombine): https://glukkazan.github.io/checkmate/turnover-variant.htm

Player vs player (PawnFreeToCombine): https://glukkazan.github.io/checkmate/turnover-variant-board.htm

I agree that this looks interesting.

I've moved the discussion over from the homepage to comments here.  I've made the link description more descriptive, and corrected some of the categories (your choices were understandable, but most of them mean something different here; something we should clarify).  The formatting of this page should be cleaned up; I can do it later if you're not up to it.

All info, games, sites and social media about Turnover Chess Variant:

Instagram: https://www.instagram.com/boardgameturnover/

Facebook: https://www.facebook.com/boardgameturnover

Blog: https://turnovergame.blogspot.com/

Youtube: https://www.youtube.com/watch?v=oQMrbXcIavQ&list=PLqgqCH3Tmc8VDLktU2graQKa2Jwi3FkHl

Play online Player vs Player: https://glukkazan.github.io/checkmate/turnover-board.htm

Play online Player vs computer: https://glukkazan.github.io/checkmate/turnover.htm

Turnover Chess Variants and dozens of other games by programmer Валентин Челноков (Valentin Chelnokov: https://glukkazan.github.io/

Ok, so the rule that you cannot destroy your own last Castle takes precedence, like in Atomic Chess. So with W: Cd1 B: Ce3, Qd2 it would be allowed to play Cxd2=C, as your new Castle would not be in check on d2.

I see there is an AI that plays this. Is that really strong, or is it just a demo?

[H. G. Muller wrote on 2019-06-25 CEST

Ok, so the rule that you cannot destroy your own last Castle takes precedence, like in Atomic Chess. So with W: Cd1 B: Ce3, Qd2 it would be allowed to play Cxd2=C, as your new Castle would not be in check on d2.

I see there is an AI that plays this. Is that really strong, or is it just a demo?]

No. CxQd2 = pawn, because castles and pawns just take diagonal forward. They dont turnover on diagonal forward, they turnover just forward. This special rule for castles and pawns I create to honor traditional chess' pawns and to balance possibilities to take Bishops, Queens and all other combinations. So pawns are like in chess, warriors tanking the enemy, just take diagonal forward and move forward, so in turnover their takes are reserved to diagonal forward move while normal move and turnover or combine with friendly pieces is reserved to forward move. Nonetheless say that the double square move from first pawn move on traditional chess is honored by same possibility to move two squares ahead by castles.

In your example, White can move ahead to turnover with Queen, but Black cannot because its not in front, so the result will be a take instead a turnover.

This is a simple AI, too weak, just for demo review.

I really apreciate your interest and comments. Thank you. I hope more people get interest too.

But d1 to d2 is not diagonal. Perhaps 'x' is wrong notation for this that confused matters.

Have a look on this example in animated gif:

https://drive.google.com/open?id=1-k8JTNaBAFNmMrd_NTB9nvfBqFhKWNTp

I think it is about your question. Thank you.

From chessvariants.com some intusiasts of turnover, asked about interesting themes. Here they are:

From wdtr2:

I am wdtr2 from chessvariants.com

Your game looks very interesting, reading the rules I have a few questions.

1) I do not know what the startup looks like

My guess (white) is

PPPPPPPP

RNBQCBNR

in the standard chess startup mode

Am I correct?

2) how does a castle move?

Guess: I moves like a king

3) What does the word disambiguation mean? I don't understand.

In your rules you said:

====================

When a White Rook in e1 combines with a Black Bishop in e5:
:Qe5 (when desambiguation is not needed)
Re1:Q5 (when desambiguation is needed)

When a White Rook in e1 combines with a White Bishop in e5:
Qe5 (when disambiguation is not needed)
Re1Q5 (when desambiguation is needed)

==========

:Qe5 and Qe5 (above) -- I think one of those has improper notation.

The text, from above, came from chess variants dot com

I feel the ":" should be mandatory. Where : means combine

Full notation would be

Re1;Be5:Qe5

Shortcut notation would be

:Qe5

Where ":" is mandatory - it means Combine

4) Can you expand the rules on splits and improve the documentation of splits?

For example: Image a Castle at e1. I am going to use the character ^ as split.

Ce1^Pe1;Qe5 Full notation where ";" is a separation character

Ce1^Ne1;Re5

5) Can you update the rules on what pieces can split into?

For example Knight can split into Pawn and Bishop

6) suggestion: I would like a rule change. Check and Checkmate do not exist. I want to introduce a new term. "Soft Check"

1) Soft check is only "on" when you have only 1 Castle

2) When you move a piece, and after the move completes, you need to say "Check". If you do not say check, you can not capture the castle on the next turn, but your move is valid.

3) With the design of "soft check", a castle may move next to a queen (even if you only have 1 castle). On the next move your opponent can not capture

the castle because your opponent did not say check. This gives the Castle a little more power, you can then always butt castles against castles. This idea is only valid, if the castle moves like a king.

7) If you only have 1 castle and you move to rank 8, it will not promote to queen.]

In Response:

​

• The startup looks like CCCCCCCC. But why this need to be like that?

  • Castles are resources

    • Players will dispose its resources along the game as they wish.

      • It adds tactic and strategy to the game, because management of resources is one of the best mechanisms to be used in strategic games.

        • Example: StarCraft, Warcraft etc.

• The King is inside a Castle.

  • But which Castle is he in?

    • He will be on last Castle. This is why players need to checkmate the last Castle.

      • sometimes is possible to checkmate more than one Castle, so the King is inside one of them.

• How does a castle move?

  • Honouring traditional chess, Castles (as they move their Pawn pieces) move one or two squares forward, just like first move of pawns on traditional chess, as well as they take pieces like pawns in traditional chess, just diagonally forward one square.

• What does the word disambiguation mean?

  • Disambiguation is about the situation where you have more then one piece of same kind able to move to a specific square, so in notation you need to indicate which piece is moving there, otherwise, when someone read the notation it will be confuse to know which piece moved there. Its is called disambiguation. See: https://en.wikipedia.org/wiki/Algebraic_notation_(chess)#Disambiguating_moves

  • Notation needs to be simple and smart at same time.

    • When we have a combination of pieces in a square, always the piece to be moved is the most outer piece, so it is not needed to say which piece move, as example when you move a Castle, of course the moved piece was its pawn piece.

    • So it is much more clever you notate moves results and disambiguate it if needed.

      • If you have a Castle in e1 and move to e3, you don't need to notation like Ce1^Pe3, but just notate e3. Because Castles are similar to pawns so you don't need to notate P as pawn and C as castle.
      • If you move a Queen in a1 to c3, you don't need to notate Qa1^Bc3, you just say Q.c3, so you look to the board and find how may you move to configure a Queen moving to c3, and if there are more than one choice, as if there is a Queen in e1, so you need to specify which Queen is moving to c3, so you notate Qa1.c3

      • Better than that and still more fun is notate combination results like when you combine your own pieces

        • If you have a Bishop in a1 and want to combine it with your Rook in c3, so you just need notate Qc3 instead of Ba1Rc3^Q. And if you have a disambiguation, like if you have a Bishop in e1 too, so to make a Qc3 is possible moving either Ba1 or Be1, so you need notate Ba1.Qc3, making big notation just to disambiguate it. But to be more clever, it can be done just notating Ba1.Qc, because Bishops just move in diagonal, so if it goes from a1 to c of course it is c3. So finally the result is Ba1.Qc.

          • And if it is not a friendly Rook, but a enemy Rook in c3, you are not performing a combination of friendly pieces, instead you are performing a turnover, the name of the game, and it is notate as two points ":", so the result notated is :Qc3 or if a disambiguation is needed it will be Ba1:Qc.

      • Can you update the rules on what pieces can split into?

        • It is not needed, because just the most outer piece is moved always, so its implicit that at least a Rook or a Bishop or both are staying behind and the possibilities on results of the moved pieces are logical.

      • Let me say that on first solution for this game there was no checkmate, but finally it gets bored, because checkmate is a very smart move, it needs much more powerful reasoning, it is so clever that computers just was able to perform a checkmate a few years ago, because its is hard to perform, so it represents the power of human mind and it needs to happen in a chess game and its variants. This is why I finally changed turnover to perform a checkmate, and the solution was imaging a King covered inside one of the castles, which turned the game much interesting because on real life in middle ages, kings sometimes fight inside its castles.

        • As you point: [Soft check is only "on" when you have only 1 Castle], it is not possible, because you may perform a situation where all castles on board get in check at same turn, so it is an impressive and beautiful checkmate. Otherwise, when you threaten just one or more castles at same time, but the opponent has other castle or castles not in check, it is not a check position. You don't need to save threatened castles if you have one or more castles not in check.
        • Just need to say check when all opponent castles are in check, and you need say checkmate if there are no possible moves to save this situation at least for one castle to keep playing. Btw say check or checkmate is not an obligatory rule in chess.
        • Castle reaching last row needs to be promoted to Queen to get not stuck there. So if you have just one Castle in e7 and a Queen in e8 or enemy Queen in e8, you cannot perform a Ce8 or :Ce8 move, because the result will be you have no castles on board anymore, by this new castle in e8 been promoted to Queen. Fascinating!

Note that saying 'check' is something amateurs do; in official games this is even forbidden. In that light it seems the following convention could be useful for this game at amateur level, to help enforcing the checking rule (which might strike ordinary chess players as unusual):

A player that attacks a castle and suspects it might be checkmate can say 'check'. This obliges his opponent to point out at the end of his next move the Castle where his King takes shelter. If that Castle cannot be captured, the game just continues, because even if there was a genuine check it has apparently been resolved. If it can be captured, the player that pointed it out could be ruled to lose, or (in a more forgiving spirit) could be obliged to acknowledge his mistake and point out another Castle (or conceed he has been checkmated or played an illegal move).

As to notation: this is not really part of the game rules, and for orthodox Chess several systems exist (descriptive notation, coordinate notation, long/short algebraic notation). I don't particularly like the notation proposed here; personally I would just stick to an existing standard, like SAN. (Also for the reason of being able to process it with existing software.) This is based on identifying a move by mentioning the type of the moving piece and the target square, possibly augmented by as many coordinates of the starting square as is needed to distinguish it from other legal moves that would be witten the same without disambiguation.

Turnover Chess offers two new aspects one usually does not have to deal with: piece types are 'fluid', and besides capture there are the possibilities of (friendly) combination and turnover. in SAN one makes the distinction between capture and non-capture by inserting an 'x' symbol, (problematic on board with more than 23 files, but then, more than 26 files would be problematic anyway...), although this is redundant, as it is fully implied by the occupation of the target square. Apparently it is considered so helpful to make this distinction jump out that it is worth the redundancy. This would then likely be true for combination and turnover as well.

My first idea was to write any move to a non-empty square with 'x', but that would not distinguish combination / turnover from true capture. It is possible to make this distinction within the existing framework of SAN, however, by using promotion suffixes: any move that would not lead to the expected occupation (i.e. the outermost ring of the moving piece) of the target square could be written as a promotion to what does result. The use of 'x' would be determined by whether the former occupant of the target square was friend or foe. So Qe3 would be a non-capture, putting a Bishop on e3, while Qxe3 would in addition have captured an enemy there (Knight, Queen, Bishop or Castle). Qe3=Q would have absorbed a frienly Rook, Qxe3=K would have turned over an enemy Pawn. In all cases a Rook would be left behind, but that is implied in this game, and so common that it does not warrant introduction of more redundant symbols in the notation.

Some more remarks: I think that using K for Knight is a really bad idea. It is mega-confusing to chess players. Even if you don't have to use 'K' for indicating another piece type, it would be better to keep N for Knight. After all, you kept the names of the orthodox pieces, while they are really not pieces at all but just constellations of rings. You might as well keep their standard abbreviations. Not distinguishing Castles and Pawns in notation is probably also undesirable (even if they move the same). So I would always mention a Castle as C, (a good reminder for what is left behind), while Pawn moves could follow the normal SAN rule of using no type indicator at all, but always prefixing a 'x' symbol with their file coordinate. This remains unambiguous here, as Pawns can only have come from 3 squares to reach the mentioned target square, and only true captures can change file.

[Note that saying 'check' is something amateurs do; in official games this is even forbidden. In that light it seems the following convention could be useful for this game at amateur level, to help enforcing the checking rule (which might strike ordinary chess players as unusual):

A player that attacks a castle and suspects it might be checkmate can say 'check'. This obliges his opponent to point out at the end of his next move the Castle where his King takes shelter. If that Castle cannot be captured, the game just continues, because even if there was a genuine check it has apparently been resolved. If it can be captured, the player that pointed it out could be ruled to lose, or (in a more forgiving spirit) could be obliged to acknowledge his mistake and point out another Castle (or conceed he has been checkmated or played an illegal move).]

• I agree we don't need to say check. Just need pay attention to checkmate, because of course if you are in checkmate, the game is over and all other move is an illegal move.
• I played a few matches with the obligation to point out every Castle under attack and I did not dislike it, but sometimes we moved a piece and did not realize that the move resulted in check on some of opponent's Castle, and I did not like can't be able to attacking this Castle for not having said check, it totally distorts game.
• Turnover allows you to checkmate in more than one Castle at same time. I've already finished a match with 3 Castles in checkmate and it's nice to talk check and check again, seeing the opponent's face when realizing there are a lot of Castles in check. I would have to test this possibility further. 
  • See it on: https://www.instagram.com/p/By00QZ9DhoG/
     

[As to notation: this is not really part of the game rules, and for orthodox Chess several systems exist (descriptive notation, coordinate notation, long/short algebraic notation). I don't particularly like the notation proposed here; personally I would just stick to an existing standard, like SAN. (Also for the reason of being able to process it with existing software.) This is based on identifying a move by mentioning the type of the moving piece and the target square, possibly augmented by as many coordinates of the starting square as is needed to distinguish it from other legal moves that would be witten the same without disambiguation.]

• I agree. Notation is a world and I just bring to myself a version to be able to take notes of my test matches to be able to animate it after. So I have learned a lot about notation and created mine. Of course each player will use his own notation system, its not a rule.

[Turnover Chess offers two new aspects one usually does not have to deal with: piece types are 'fluid', and besides capture there are the possibilities of (friendly) combination and turnover. in SAN one makes the distinction between capture and non-capture by inserting an 'x' symbol, (problematic on board with more than 23 files, but then, more than 26 files would be problematic anyway...), although this is redundant, as it is fully implied by the occupation of the target square. Apparently it is considered so helpful to make this distinction jump out that it is worth the redundancy. This would then likely be true for combination and turnover as well.]

• Well, the two points ":" I used to highlight a turnover, was just marketing :) Thinking in a future where two points is a kind of trademark, icon or turnover brand. Its not essentially needed. We don't need to differentiate if it is a friendly combining or a turnover.
• x mark is so cute :( it gives dopamine :) when you take an opponent piece. I agree it can be redundant. If I take, instead use x to indicate a take, just notate which piece is seated on square gives the same result and x will be unnecessary. I will try notate some matches to see it better.

[My first idea was to write any move to a non-empty square with 'x', but that would not distinguish combination / turnover from true capture. It is possible to make this distinction within the existing framework of SAN, however, by using promotion suffixes: any move that would not lead to the expected occupation (i.e. the outermost ring of the moving piece) of the target square could be written as a promotion to what does result. The use of 'x' would be determined by whether the former occupant of the target square was friend or foe. So Qe3 would be a non-capture, putting a Bishop on e3, while Qxe3 would in addition have captured an enemy there (Knight, Queen, Bishop or Castle). Qe3=Q would have absorbed a frienly Rook, Qxe3=K would have turned over an enemy Pawn. In all cases a Rook would be left behind, but that is implied in this game, and so common that it does not warrant introduction of more redundant symbols in the notation.]

• Just write the result is good. Instead QxQe3, just Q.e3 as I write or Qe3 is fine, but less exciting in therms of x as "hey have you seen? I take it!". I use a point to diferenciate move and combination, Q.e3 = "Queen moved to e3" so it is its Bishop going to e3 and Rook left behind... and Qe3 = "A Queen was mounted in e3", so evidently there is a Rook in e3 to be able to perform Qe3. I like it.

[Some more remarks: I think that using K for Knight is a really bad idea. It is mega-confusing to chess players. Even if you don't have to use 'K' for indicating another piece type, it would be better to keep N for Knight. After all, you kept the names of the orthodox pieces, while they are really not pieces at all but just constellations of rings. You might as well keep their standard abbreviations.]

• I like it. N is better. Friends said I need keep distance from chess, so I suppose use K was a way to try keep this distance, but N is good. 

[Not distinguishing Castles and Pawns in notation is probably also undesirable (even if they move the same). So I would always mention a Castle as C, (a good reminder for what is left behind), while Pawn moves could follow the normal SAN rule of using no type indicator at all, but always prefixing a 'x' symbol with their file coordinate. This remains unambiguous here, as Pawns can only have come from 3 squares to reach the mentioned target square, and only true captures can change file.]

• I have tested it a lot, and it is really not needed to diferenciate C and pawn. When I start a match I just write a3 and it is a Ca1 goint to c3. 

Here is a version where Pawns turnover Bishops and Queens in diagonal forward. This change was made to test this variation rule in how pawns must handle takes and turnovers. Check it up!

https://glukkazan.github.io/checkmate/turnover-variant-board.htm

Special thanks to: Jim Diego, from skype discussion. Skype: boardgameturnover

Initially I liked the logic of treating recombination/turnover as a non-capture, and true capture as a capture. But when I was thinking about notation, it struck me as even more logical to only treat the recombination as non-capture (i.e. straght Pawn moves), and turnover and true capture as capture (i.e. diagonal Pawn moves). Because only the latter two move types really gain anything; the recombination you can undo any time you want. So recombination is more like a noncapture, where you happen to be allowed to stay with multiple pieces in one square. My SAN notation scheme would only use 'x' for true capture and turnover (the latter with promotion suffix).

I have no idea whether this would actually make a better game. And it is of course silly to let convenience of a notation system influence the rules. But is strikes me as more elegant.

Here is a match with Pawns handling turnovers on diagonal forward:

https://www.youtube.com/watch?v=hyppzlkwjj4&feature=youtu.be

I played a few matches with the PawnFreetoCombine version and I have to be honest, I can not play the previous version again. Much more intuitive and uncomplicated, definitely elegant and sincere. I will change this rule soon.

Probable new variant rule: Castle in check, move like chess King.

After hundreds of Turnover matches I have done, I finally realize that something is missing in the context of game logic. Since in traditional chess, at least two pieces are needed to perform a checkmate, with few exceptions on stucked Kings, I realize that this kind of complexity on checkmates is needed on Turnover too. So, I found a way to let it works, featuring the rule where a Castle in check, move like a King from traditional chess. It can move and take one square all around it.

The results is incredible, games have grown in logical complexity and I dare to say that finally it is better than chess.

Now I am discussing it with my developer to bring us a version with this change, so we all can test it. See on: https://www.facebook.com/groups/turnoverchess/permalink/3357003974392091

Enjoy.

The most recent change to this page removes all description of the rules, directing the reader to an external site. This seems undesirable.

This is the most original and inventive chess variant I ever encountered, and I like that very much. I agree that the current submission is not suitable as a rules page, though. We do have pages for external links, and it can be used as one of those. But it would be a pity if there is no full rule description of Turnover on this site.

That accessing the rules link requires a login is of course a deal breaker...

The author, Lúcio José Patrocínio Filho, has updated this page.

The link now points to an accessible website. But this website unfortunately contains a very incomplete rule description. The most essential part seems to be missing (namely that a move consists of moving only the outer-most ring of a combination).

(Unfinished) test Diagram:

Ughh! Trying to implement the turnover transformation and splitting rules through a custom xxxTinker script revealed a bug in the parsing of the captureMatrix. Instead of ignoring promotion to its own type, it ignored promotion to the type just before it in the table.

After fixing this, I think I got the normal moving right. Promotion is still to be done.