This document presents first a variant which is colorbound to the maximum extreme, so much so that you can't get more colorbound than that, so much so that it deserves to be called Colorboundmost Chess; and after that you will find a variant which is extremely colorbound but which is designed so that the weak interactions between the colors make the game more interesting to play than the extreme of Colorboundmost Chess.
In the endgame, opposite-colored Bishops often produce a draw because the Bishops are so innefective on each others' colors; but if there are Rooks or even Queens, opposite Bishops are far from drawish because they enable attacks on squares of one color. The Bf8 cannot defend f7!
Beyond the colorboundness of the individual pieces, there is also the colorboundness of the game to consider. The most extreme degree of colorboundness is attained when the pieces on dark squares can never interact in any way with the pieces on light squares.
The most colorbound game can be played on two separate chessboards, one using the light squares and one using the dark squares. In fact, it really ought to be played that way, because the visual clutter of having both colors of square occupied may be construed as a form of interaction between the colors. However, one is not required to use two chessboards; this is merely a suggestion.
Castling cannot be in the game because O-O-O moves one piece on each color and changes the color of one piece. This is too bad, because Castling makes the chess more interesting.
The game must be played as a doublemove game! Each turn, each player makes one move on a light square and one on a dark square. In a single-move game, each turn each player must decide whether to play on light or on dark; and although this interaction between the colors would make the game more interesting, it is an interaction between the colors and so we cannot have it in Colorboundmost Chess.
(If you are stalemated on one color, the game is a draw. If you have no pieces at all on one color, you are not stalemated even though you have no moves on that color.)
The rules above are sufficient to define the game even without deciding what pieces are in it. The next step is to think about the characteristics of the game.
Characterizing the game as a race makes one think of the fair race rule used by V.R. Parton in his game Racing Kings: Black gets one turn at the end to equalize and draw -- in Colorboundmost Chess, this would mean that if Black can reply to checkmate with a checkmate, the game is drawn. Unfortunately, symmetrical play would guarantee a draw!
Therefore, the rule to equalize the race must be borrowed from Balanced Doublemove Chess: on White's first turn, W may make only one move. In Colorboundmost Chess, we must add to this rule and say that White's first turn must be a single move on a dark square, that is, on White's defensive color.
This possibility can add interest to the game, so the game designer adds this to the game; besides, there's no other game with a half-draw, and I always like to put in something completely new!
The idea is, suppose that you see mate is inevitable on your defensive color, but first you can force perpetual check on your offensive color; instead of losing 1-0, you lose by 3/4 to 1/4!
This rule applies only to stalemate or to perpetual check or to triple repetition of position; it does not allow you to claim a half-draw by lack of mating material.
Checkmate ends the game, and if a half-draw has not occurred on the other color, checkmate wins by 1-0; but if there has been a half-draw, checkmate wins by a score of "0.75-0.25".
The interesting thing is that these rules were derived by pure logic from the original premise, without the slightest reference to the actual powers of the pieces.
The Colorboundmost King moves and captures as Ferz plus Dabbabah. (Remember that Castling is illegal). If you want to try using this army against the regular FIDE army, you should use a standard King.
Colorboundmost Pawns move and capture as fF, forward Ferz, and on reaching the 8th rank get promoted to any non-royal piece that was in the game at the start. The initial double step is two squares diagonally, and en passant works as expected.
The Queen should be Crooked Bishop plus Bishop, but the duplication of the Ferz move in the Colorboundmost Queen's two components makes this piece weaker than desired. Therefore I add to it the power of moving as DD, Dabbabah-rider (a piece that makes repeated moves in the same direction as a Dabbabah); perhaps also Alfil-rider should be added, but DD should be enough.
The following diagram shows the Queen's moves:
Squares reached by the Bishop's move are marked with a b, squares reached by the Crooked Bishop's move by a c, and squares reached by the Dabbabah-Rider's move by a d.+---+---+---+---+---+---+---+---+ | b |:::| |:::|c d|:::| |:::| +---+---+---+---+---+---+---+---+ |:::| b |:::| c |:::| c |:::| b | +---+---+---+---+---+---+---+---+ | |:::| b |:::|c d|:::| b |:::| +---+---+---+---+---+---+---+---+ |:::| c |:::|b c|:::|b c|:::| c | +---+---+---+---+---+---+---+---+ |c d|:::|c d|:::| Q |:::|c d|:::| +---+---+---+---+---+---+---+---+ |:::| c |:::|b c|:::|b c|:::| c | +---+---+---+---+---+---+---+---+ | |:::| b |:::|c d|:::| b |:::| +---+---+---+---+---+---+---+---+ |:::| b |:::| c |:::| c |:::| b | +---+---+---+---+---+---+---+---+
The most interesting alternative is Ferz plus Langskip (wide forward (1,3) leap plus narrow back (1,3) leap -- fsLbbL), which would be a Knight substitute and which is somewhat stronger than the FA. Let's name this piece the Raider.
+---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| |:::| |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| + |:::| + |:::| + |:::| + | +---+---+---+---+---+---+---+---+ | |:::| |:::| R |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| + |:::| + |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| + |:::| + |:::| | +---+---+---+---+---+---+---+---+
In order to make the game even more interesting, some weak interactions between the colors may be allowed.
First of all, it should be a normal singlemove game; and of course, both colors must be on the same chessboard. (If you are stalemated on one color but you have a move on the other color, of course the game is not stalemate.)
Castling is permitted, and O-O-O must keep the King on its original color; this means that when you castle Queenside, the Crooked Bishop on a1 moves from a1 to d1, giving you one more attacking piece but one fewer defensive piece! This is a risky decision which adds to the possibilities of the game.
The Nearly Colorboundmost King becomes a lame jumper: it cannot, for example, move from e1 to e3 if e2 is occupied! This is an important interaction between the colors because it affects the King.
Instead of Colorboundmost Pawns, the game of Nearly Colorboundmost Chess uses Berolina Pawns -- which change color when they capture! For this reason, the decision to make a Pawn capture will require extra thought.
That is all. These four rules changes should make Nearly Colorboundmost Chess even more interesting to play than Colorboundmost Chess.
A Bishop can cut off the opposing Colorboundmost King, very much the way a Rook can cut off the enemy King in FIDE Chess: for example, suppose we have WBg2, WPe2, and BKe8. The King can never cross the diagonal, nor can it ever attack a6. Therefore the Pawn advances easily to promotion.
The position with WPa6, WBf1 and BKa8 is zugzwang in the doublemove game of Colorboundmost Chess, but is a draw in the singlemove game of Nearly Colorboundmost Chess. White cannot advance by force; In the doublemove game, Black would be forced to move Ka8-c8, allowing Bf1-g2 winning; but in the singlemove game, Kb7 is legal because Berolina Pawns are used, or instead Black could make a move on the other color.
However, the endings with Colorboundmost King versus Colorboundmost Pawn turn out to be interesting.
For example, with WPd3, BKd1, and White to play, the game is an easy draw; for example, 1. d3-e4 Kd1-d3 2. e4-f5 Kd3-e4 [....] 4. g6-h7 Kf5-g6 and the Pawn is trapped by the edge of the board.
This is the key to all endgames with Pawns, for example WPe4 WPd3 BKe6, Black to play, you should be able to figure out how to draw.
Likewise, an endgame with FA plus Pawn versus King becomes easy to understand once you know the key position of King versus Pawn.
Nearly Colorboundmost Chess is designed to be much more than a race to mate; although the race is present, and although the race means that you cannot have the full flavor of FIDE Chess (specifically, the dry endgames are usually absent), the weak interaction between the two nearly separate simultaneous games gives this game a unique interest and a flavor all its own.