Fergus:

To help you spot the bug that is in our Colossus game here is part of the program:

Syntax Error on line 673

 658 MOVE: r i3-j3
 659 postauto2
 660 moveindex 146
 661 MOVE: B h1-j3
 662 postauto1
 663 moveindex 147
 664 MOVE: q g3-j3
 665 postauto2
 666 set posvar join "b" join fencode boardflags
 667 if >= var #posvar 3
 668   say Three Times Repetition! Drawn Game!
 669   drawn
 670 elseif sub stalemated #K
 671   if sub checked #K
 672     say Checkmate! Black has won!
 673     won:
else:
say Stalemate! The game is drawn.
 674     drawn
 675   endif
 676 elseif >= #nopvc 100
 677   say Fifty Moves Without Moving a Pawn or Capturing! Game Drawn!
 678   drawn
 679 elseif sub checked #K
 680   say Check!
 681 endif
 682 end

I understand the problem is the two points after the "won" word.

Ok, sounds good.  I will assign the games for round 2 on Saturday afternoon.

OK... Thanks!

Thanks. Good luck to everyone!

[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.

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?

Could be that I did that intentionally. The universal leaper moves are generated by a piece of code that is completely different from the code that generates other moves. (As they are not relative to the start square.) And this code doesn't test for the target squares being attacked. In the Maka Dai Dai Shogi diagram the Emperor was the only royal piece, (as it was the last piece mentioned), but I did not want any royal piece, (as there is no rule against putting yourself in check there), and the fact that it is a universal leaper now hides this. But later I added commands to the diagram to set the royal piece by hand, and allow multiple or none. So this kludge is no longer needed.

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

I remember this happenning to me, too!

I wanted to get to it but I still have not been able to take the time!... :(

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.