Comments by thomas

I propose the theme of a draw- and tie-free chess.

If the mechanism of a game allows repetitions, one needs a rule to deal with them, and players have to keep track of the positions occuring in the game. This is not always easy. In an endgame with Queens, e.g., one might chase the opponent's King several times round the board. Then have fun remembering all the previous positions, not to overlook a repetition.

Also, if repetitions are possible, this usually means that the game can last an exponential number of moves. As an upper bound for the game length, one can count all legal positions with the given pieces on the board (with pawns remaining where they are), and the number is usually gigantic. To break such ties, the artificial and ugly 50-moves-rule (or something similar) is needed.

So I find it desirable to invent a Chess variant with a playing mechanism which can't lead to repetitions. A simple example would be that pieces can move only forward, as in the game of Breakthrough.

This variant I find very interesting.

Additional idea: let the pieces make a non-capturing move laterally or
backwards with demoting the piece to the next lower kind, e.g. in the
order queen -> rook -> bishop -> knight -> pawn. This is buying more time,
and also combinations may include the demotion of a piece to alter its way
of moving.

The king is maybe too vulnerable in these variants. A defended Queen on
any of the three squares in front of the King mates, and also a defended
rook directly in front of it. Three pawns can also mate.

One might add the rule that the king may also move laterally or backwards
when attacked. I think this does not lead to cycles, but if there are
Rooks and Nightriders, a cycle is possible:
white: King e2, Rook e1
black: King e5, Nightrider f7
1. Kd3+ Kd6+
2. Ke2  Ke5

I have written two presets:

http://play.chessvariants.org/pbm/play.php?game%3DBreakthrough%26settings%3DBreakthrough

http://play.chessvariants.org/pbm/play.php?game%3DSquirrel+Chess%26settings%3DSquirrelChess1


May I ask some questions about Game Courier / GAME code:

1. I observe that I can't enter comments starting with '//' in the
Pre-Game part. I wrote:

// comment
setsystem maxmove 2;
...

And I receive an error message:

Syntax Error on line 0
// comment
setsystem maxmove 2 is not a valid expression, because // is not a
recognized piece, coordinate, command, or subroutine.

Why is this?


2. What happens if I edit and save a preset if there are already players
using it, e.g. when I remove a bug or add notification for mate /
stalemate. Can this cause problems?


3. What happens if an operator needs more operands than are on the stack,
or if there are two or more values left on the stack after evaluating an
expression, or if an operator is given an operand with a senseless type,
e.g.:
  set ep false;
  ...
  if equal where #ep 0 1 a3;
    ...
  endif;

Are there rules how such cases are handled, or does the program behave in
an undefined way?


4. am I right that a board position (like 'a4') is of type 'string',
and also a piece type like 'n' or 'K'? Or are these special types on
their own?

I have read about a different variant of Atomic Chess in the book
'Alternatives Schach' by Lars Döring (german):

After a capture, the capturing piece and all pieces on the squares
orthogonally or diagonally adjacent to it are also removed, but with the
exception of the kings. A king may capture without being removed, and is
not removed when on a square adjacent to the capture.

A move may never put the King of the moving side into attack, neither
before nor after removing of pieces. So a king may never capture a
defended piece, even if the defending piece would also be removed.

In this variant, the initial advantage of white is much smaller.

I want to restrict user input so:

setsystem maxmove 2;
ban commands allmoves;
allow moves 1 moves 2 captures 1 promotions 2;

The purpose is to allow entering a generalized castling move, examples:

e1-d1;a1-e1
e1-b1;a1-d1

But then the user might enter something like c1-f7;d2-d4 , the first part
being illegal. The preset should reject this move, but it is difficult,
because the system variables only reflect the (legal) second part d2-d4 :

old = @
origin = d2
dest = d4
moved = P

Is it possible to get info about the first move-part, or at least the info
that the user has entered two parts?

1. The description doesn't make it clear that the center of a piece can be
on one of the side rows (a, t, 1, 20). This means that Black may start the
game with the move a3-b3. See
http://www.archim.org.uk/eureka/53/gess.html.

2. I don't know if it is allowed to move the center of a piece onto a
side row. Is black allowed to start a game with r3-t3, capturing four of
his stones? Or can a piece move only so far as to move the direction stone
onto a side row?

Sorry I have to pester you again:

I'm writing a preset for Wildebeest Chess.
Now I have a strange bug in the code which I can't understand. I have
boiled it down to the following little procedure:

sub test;
  my i;
  set i origin;
  do:
    if != space #i @:
      die X.;
    endif;
    set i where #i 0 1;
  loop until == #i dest;
endsub;

This is defined in the pre-Game part. In the Post-Move-1 part I call the
procedure:

gosub test;

Then I enter a pawn move, e.g. f2-f5 and I get the error message
'misplaced endsub' at the line number where the procedure 'test' ends.
Why is this?

One might add a one-space orthogonal step to the Knight (Wazir Knight) and
a one-space diagonal step to the Camel (Wizard from Omega Chess), and both
moves to the Wildebeest (Wildebeest plus King). This preserves the symmetry
between the riding and leaping pieces, and now the King is integrated into
it, having the moves which are shared by Queen and Wildebeest.

And the stronger pieces can be seen as a second advantage, if one feels
that the standard pieces are relatively weak for the big board.

I suggest to use a pie rule: The side without king is made stronger (like
in the first game where black has a queen for the king), and one player
sets the maximal number of moves to mate, then the other player chooses a
side.

I'm done with four presets yet. They are automated and with
rule-enforcement and detect the end of a game (but not by threefold
repetition or 50 moves rule). I have tested them and they seem to be
bugfree. Maybe you want to include them into the 'Games for Game
Courier' list.

Breakthrough:
http://play.chessvariants.org/pbm/play.php?game%3DBreakthrough%26settings%3DBreakthrough

Wildebeest Chess:
http://play.chessvariants.org/pbm/play.php?game%3DWildebeest+Chess%26settings%3DWildebeest+Chess+with+rules

Gess:
http://play.chessvariants.org/pbm/play.php?game%3DGess%26settings%3DGess+with+rules
Playing gess is a nuisance without an automated preset, so I wrote one. To
make the point-and-click movement usable, the preset expects that the
origin and destination coordinates of the direction stone are entered.
This is uncommon, normally a move is denoted by the coordinates of the
center of a piece (= 3x3 area containing a stone in the direction of
movement).

Squirrel Chess:
http://play.chessvariants.org/pbm/play.php?game%3DSquirrel+Chess%26settings%3DSquirrelChess1
This variant I have made up myself. The difference to orthochess is only
the 9x9 board and every side has an extra pawn and a squirrel which leaps
two squares orthogonally or diagonally or like a knight (as described in
the piececlopedia). Pawns promote to squirrels also.


BTW: how can I uncheck 'exclude pieces not in setup' when editing a
preset? Somehow it doesn't work.

Is it possible to select some pieces out of a piece set and assign them 
names entirely of upper- or lowercase letters, so that 'isupper' and
'islower' can be used to identify pieces of a side?