Ratings & Comments

It works now.

Respect the power of three Wazirs - they can checkmate a lone King in 47 moves.

True. But not very relevant. Three Ferzes do it faster when not all on the same color. (Addmitted, this rules out 1/4 of the cases.) But in Shatranj stalemate is a win, and even two Ferzes or Wazirs can force that on a bare King. And the worst case for the Ferzes is two moves faster than for the Wazirs, even when they are on the same color.

This page is now ready for review, please.

Unfortunatey a general t modifier is a bit hard to implement. Which is a pity, as with the unload modifier it would make it possible to describe magnetic pieces and catapult pieces.

So for now I added capture of pieces adjacent to the destination as a standard feature, controllable through the capture matrix and from WeirdPromotion(), as internally it uses the promotion element of the move array to trigger it. An @ in the captureMatrix orders promotion to piece number 512 for that particular combination of attacker and victim (wher the latter can also be an empty square). Now this is an invalid piece number, and used as a kludge to indicate 'burning'. How exactly this burning works depends on a new parameter atomicCapture=N. For N=0 it does Tenjiku-type burning: only enemies get burned, and the capturer survives. For larger N is gives you explosion like in Atomic Chess: all adjacent pieces are destroyed, friend and foe alike, but the first N piece types from the table survive, while the capturer always selfdestructs.

Now this works the same when you return 512 from WeirdPromotion(). But you have additional control there. By returning 512+C (0 < C < 256) you also trigger the burning. But in that case it burns only the squares selected through the bits of C, where 1 = N, 2 = NE, 4 = E, 8 = SE, etc. So WeirdPromotion() could do additional testing on the board to decide whether an adjacent piece should be burned or not. This could for instance be used to implement Ultima Pincher Pawns, by checking whether there is a friendly piece behind the adjacent one.

All this only works with newClick=1, which unfortunately means that the move diagrams (using the old highlight code) would not show the burning. It is not easy to cure that, as the move generator doesn't know about it (as far as that it is just a promotion), and no clicks on the burn victims are required . (During hovering over the move diagram the highlighting is as if the hovered square had received the second click, and it shows where the third can go.)

BTW, I now added a link to the Extended Betza article.

Now I see what you mean. I don't think it is something I have done!

Since people keep wanting to use tags for information that is already stored in the database, I have modified the footer script to include categories and board dimensions just above the tags section.

Respect the power of three Wazirs - they can checkmate a lone King in 47 moves. Also, I think the position in the diagram can be reached, leaving the Black Alfil limited to two squares: (e2) and (g4). Surely White can eventually force a trade of one Wazir for the Alfil. Question: would replacing the Alfil with an Alibaba (A+D) save the draw for Black?

What would be an appropriate tag for hexagonal boards?

Back in [2018-03-04] Kevin Pacey mentioned "the pleasing possibilities of smothered ... mates".  My 12x12 variant Rose Chess XII has 96 empty squares, with ten Pawns each on the 4th and 9th ranks.  But Black can deliver a smothering mate with a circular Nightrider on the second move of the game.  A position so amusing that it earned a diagram at the top of the rules page.

Speaking of XBetza (or rather, IBetza), you should really consider adding a link to your page on Extended Betza Notation to this page. Even if it is not strictly identical to the one used in the interactive diagrams it would be a very helpful edition. I did check for a link to that page before writing this, and I couldn't find one.

The new definition for t could be quite interesting. It also helps that kc covers the old function of t (excluding capture of royals).

Similar to Courier-Spiel, the game adds modern Bishops and improves the Elephants (called Couriers here). Switching the Bishops and Couriers in the initial setup will improve this game. While the b-file and h-file Pawns are now undefended, they are also no longer threatened by hostile Bishops. Jumping the Courier c1-c3 will help to shield the Pawn on (b2).

Some time before 1992, Paul V. Byway included the Ferz in Modern Courier Chess, placing RNCBFQKFBCNR on a 12x8 board. Ken Franklin also placed Alibabas in Leap Chess on 44 squares.

The diagrams on this and the Apothecary Chess-Classic page are missing white's brouhaha squares, and so are both corresponding game courier presets.

I'm not quite sure whether I want to rate this Good or Excellent so I'll go with the higher rating. This is a great way to enhance weaker pieces without making them too strong. An interesting variation of this idea might be to have all the pieces except the king and queen start without their non-capturing king moves and gain them by promoting on the last two ranks.

True. But I have always had the feeling that XBetza notation should be the vehicle to specify that, not the promotion. What I am missing in XBetza is the possibility to specify a side effect that is mandatory when possible, but not blocking the move when impossible.

How about this: the modifier t is a leg separator like a, except that the actual piece move terminates at that point, and the remaining legs only describe the path of its 'influence'. If this is not a unique continuation, all possible realizations will be combined with the move. So where yacabQ would describe a Queen that (by virtue of the y) does a single King-like burn of an enemy, ytacQ would burn every enemy adjacent to the square it lands on, and can even land there if there is no adjacent enemy at all. An Ultima Pincher Pawn would be ytacfapR, where the captureMatrix would be used to forbid the piece (and its influence) to hop an enemy. Unlike actual moves, the last leg of the influence can be a 'hop-on' leg.

If you are prepared to use JavaScript there are many ways you could interfere with the standard operation of the Diagram. There is for instance a routine ScoreMove(move, predecessor), to prep the 'raw' moves coming out of the move generator by determining the piece types of the capture victims, storing those in the array describing the move, and calculating the effect these captures (and promotions) would have on the score. ('predecessor' is the move preceding it, only used to enforce anti-trading rules). Interfering there to add a few burn victims is not very difficult; you just replace the function by a wrapper for it, like:

var OriginalScoreMove = ScoreMove; // remember the standard routine
var burnX = [ 1, 1, 1, 0, -1, -1, -1, 0 ];
var burnY = [ 1, 0, -1, -1, -1, 0, 1, 1 ]; 
function ScoreMove(m, last) { // and redefine it
  var x = m[0], y = m[1];     // origin
  var piece = board[y][x];    // moving piece
  if(IsBurner(piece)) {
    var n = 4; // 0-3 are the coordinates of origin and destination
    for(var k=0; k<8; k++) {
      var xb = x + burnX[k], yb = y + burnY[k]; // coordinates of neighbor square
      if(IsEnemy(xb, yb)) { // this is assumed to return 0 when (x, y) is off board
        m[n++] = xb; m[n++] = yb; // add a locust victim
        m[-2]++; // this counts the number of squares in the move
      }
    }
  }
  return OriginalScoreMove(m, last); // call the standard routine on the modified move
}

Positions like this suggest that promotion to colorbound pieces is a poor design choice.

One could also argue that promoting to the weak, color-bound Ferz enriches Shatranj with an interesting strategic theme: one has to plan Pawn manoeuvres such that you won't promote all your Pawns on the same shade. And definitely do not leave the opponent a defender on the other shade when you are playing for a win. This is already true in orthodox Chess, where unlike Bishops can draw even against a majority of 2 Pawns, despite the fact that these would promote to Queen.

It is true that Shatranj is quite drawish, but I think this is more a consequence of the Ferz being such a weak piece than of its color-binding. I doubt that promoting to Wazir would be much of an improvement.

Kamikaze pieces are a form of promotion (namely promotion to an empty square). The Interactive Diagram does support mechanisms for indicating unusual promotions (like the captureMatrix), but unfortunately promotion to empty is not amongst those. The problem is that promotion code 0 (the code of an empty square) is used to indicate there is no promotion, and the piece remains itself.

It should be possible to use another code for indicating promotion to empty, though, and recognize that as a special case in the routine that performs the moves.

The ShowMoves problem appears to occur because this still uses the old highlighting routine. And now that I leave out the loop directive from the internal move descriptors this cuts non-final slider legs with m rights (which should continue after a succesful try) to their first step. I should make the highlighting in ShowMoves also be done with NewClick(); I guess I didn't do that because it never has to deal with a double locust capture, as hovering gives you at most a single potential victim.

A reasonably cheap method for tracking pieces (of all types!) would use an array location[] indexed by (colored) type, where the square numbers (calculated as 128*rank + file) where pieces of a given type sit would be stored in location[type] and location[type+512]. This can be updated in MakeMove() like

function TrackMakeMove(m) {
  var p = m[-6] & 1535; // moving piece (stripped of marker flags and virginity)
  if(location[p] == 128*m[1] + m[0]) location[p] = -1; // mark first entry as invalid when it was for the moved piece
  p = m[-1] & 1535; // promoted type (could be same as mover)
  if(location[p] < 0) location[p] = 128*m[3] + m[2]; // put destination in first entry when the latter was unused
  else location[p+512] = 128*m[3] + m[2]; // otherwise it must have been for the other piece of this type, so this piece uses second entry
  OriginalMakeMove(m);
}

and similar for UnMake(). It would not take account of capture of the pieces, (which would be cumbersome because of the possibility of locust capture), so when using the locations for a type it should always be tested whether a piece of that type is actually there; it could still indicate the square where a piece of that type was captured, but which now is occupied by something else.

Limitation is that it would only work if there are at most two pieces of the types of interest. Which for Suzumu Shogi would not be the case, as there could be four Tetrarchs. But somehow it doesn't seem wise to adapt a general feature to a very exceptional case; in virtually every variant there are only two pieces of each type. One could always artificially make the Diagram use two different Chariot Soldiers and Tetrarchs, each present as a pair. After all, we already artificially distinguish a Lion Hawk obtained through promotion from a primordial one, just to maintain a homogeneous mapping from piece to promoted form.

With the aid of this you would only have to look for enemy Tetrarchs in 4 locations, rather than 256. You would do that in BadZone() when you find 'nodes' increased, and for every Tetrarch you find this way you would set the square surrounding it to 'nodes' on an auxiliary board. Moves starting from a thus marked square would then be suppressed, as that piece would be frozen.

This diagram shows a boring draw from Shatranj. If the White King moves towards (f3), then the Alfil can simply go back to its home square (c8). Positions like this suggest that promotion to colorbound pieces is a poor design choice. Try substituting three Champions (Silver Generals) and one Dragon (Ferz+Alfil). Now White can play

1. Champion a7-b6 check, King b7-a6

2. King d6-c5, Dragon g4-e6

3. Champion b8-a7, Dragon e6-c8

4. Champion a7-a8, ignoring the Bare King/stalemate victory and intending checkmate after moving to (b7). An FIDE Bishop (replacing the Dragon in the initial position) might be able to trade itself for a Champion and make White settle for a "mere" Bare King or stalemate victory. Some thoughts on piece values:

Rook=15, Bishop=9.5, Knight=9, Silver General=8.5, Ferz=5, Alfil=4, Pawn=3