The rules are the same as in conventional chess, but only moves in which the pieces advance toward the back rank of the opponent are legal. No piece can ever go back or sidewise.
It has the advantage that implementation is very simple and the game is played in an attacking style, it progresses rapidly, draw by repetition is out of question.
This is a completely random example game:
http://en.lichess.org/CxR7tvKu#4422. ... d3+ is now mate, because white king can only go sidewise or back to get out of the check and the pawn giving the check can only be taken by a backward move of the bishop or a sidewise move of the rook.
I think this variation is kinda silly, there is no attack in going forward.
Anyway, watching your game, I can't understand why the Queen is never captured, and even according to your rules, if Queen capture the Rock would be checkmate. I don't understand anything.
This whole thing came out of me generating completely random 100 move games with the computer. I wondered how such games look like. What struck me is that mate in random games is very rare. I had to generate at least ten 100 move games ( 200 halfmoves ) so that there is a random mate within the first 100 moves.
I was trying to find an algorithmic way to give some forcing direction to the game and going forward is a condition that can be implemented very easily: you just have to compare the ranks of the moves and filter the move list for moves in which the target square has a higher rank then the initial square.
Immedeiately the games started to end very quickly either in mate or stalemate. Very seldom do random forward going games last more than 30 moves. The example game has been generated this way.
The length of the games are limited, because there are limited number of forward going moves available.
It would be interesting to see forward going bullet games, since you cannot move pieces back and forth just to gain time. The game is more likely to reach a decisive result rather than timing out. Finding legal moves is much more difficult so you are forced to think even in bullet games.
#3 Finding legal moves is sometimes hard enough already during time scrambles. haha
I was making some calculations as to what contstraints this rule puts on games.
1) First of all the number of moves is limited. A mindless upper bound can be obtained by considering that all pawns can make at most 6 moves ( a total of 6*8=48 pawn moves ), all pieces can make at most 7 moves ( making for 7*8=56 piece moves ). Therefore the game cannot last longer than 48+56=104 moves. However pawns cannot fly over each other, so you need 4 captures to be able to use the maximum amount of pawn moves. Each capture takes away two moves, that is 8 moves alltogether. So the game cannot last longer than 96 moves.
2) Casting is a lateral move, therefore illegal.
3) Promotion is possible but promoted pieces stay where they are, they cannot make any further move.
4) Pieces attacking the king from the behind or side cannot be taken by the king even if on adjacent squares and even if unprotected. In one of the random games that I genreated the queen was mating alone from the behind, quite spectacular, as if it was Atomic chess.
Is this purely for fun or do you identify any benefits for standard chess play through it?
This sounds interesting.