Humpty Dumpty Chess

First I decided that the game should use the Colchester Latrunculi board of 12 files by 8 ranks - coincidentally the same dimensions used in Courier should you wish to see such a board in use - and use FIDE pieces and Cannons. With this combination it seemed sensible to add Yang Qi's Arrow in. The start of Humpty's name, combined with one of Lewis Carroll's own verse works mentioning "a camel with a hump", and Colchester's ancient name of Camulodunum, suggested that Camels too suited this game. This mix of pieces recalls my Wildeurasian (WEA) Qi, but I could not connect the Gnu with any aspect of the theme and there were certainly no tanks in the siege! I therefore decided to exclude compounds of duals - even a Queen - from the array, but introduce them later by promotion. Where the array might otherwise have had them I put the Frog which I use in CoBlaChe, a Double Cross Besiege subvariant also set in the East Essex lowlands - and which is also a recurring motif of Lewis Carroll's works.

It seemed to me that a variant set in Europe shouldn't be too like Xiang Qi. I chose a front rank of Pawns, but with XQ-like gaps mainly to keep representation simple. I followed the WEA Qi pattern of two FIDE sets - one representing themselves and the other with Knights as Camels, King as Gnu, and linepieces in Hopping-capture form. The second set's Pawns would represent Frogs. The Essex river Colne (the Co of CoBlaChe) played a major part in the siege but neither of my Anglis Qi River rules suited this variant. The Bishop's run-up was specific to that variant, whose name has echoes of a neighbouring and rival region, so Essex locals might resent the connection. Early Pawn promotion is also used in offshoots, but the array already has pieces represented by the second set's Pawns. Eventually I decided to make the River a restriction on that latter piece, reflecting how bridges were guarded in the siege.

Setup

Pieces

The KING moves one step in any radial direction and must be kept out of Check.

+=	The ROOK moves any distance through empty intermediate cells in any of the 4 orthogonal directions, and the BISHOP does likewise in the 4 diagonal directions. The QUEEN is the compound of these two, moving in all 8 directions.
+=	The KNIGHT leaps to any of the 8 cells 2:1 away from it, and the CAMEL to any of the 8 cells 3:1 away from it. The GNU is the compound of these two and can leap to all 16 cells. None of these pieces can be blocked.
+=	The CANNON differs from the Rook, the ARROW from the Bishop, and their compound the TANK from the Queen, in that capturing moves require exactly one intervening piece, which is of either army and not itself captured.

	The FROG moves one step diagonally or three orthogonally. As these moves are bound independently it is itself unbound, and it can lose the move in five moves (one along a rank, one along a file, and three diagonal in any order). Within either player's half of the board the orthogonal component is an unblockable leap but note the River rule in the next section.
	The PAWN moves one step forward at a time, diagonally if capturing otherwise orthogonally.

Rules

The boundary between the fourth and fifth ranks is a River that Frogs can cross only if there is no intervening piece of either army.

The following pieces may be promoted when reaching the far rank from another rank.
* Pawn or Frog to Queen if the player has no Queen on the board at the time;
* Pawn or Frog to Gnu if the player has no Gnu on the board at the time;
* Pawn or Frog to Tank if the player has no Tank on the board at the time;
* Pawn to Frog if the player has a Queen, a Gnu, and a Tank on the board at the time.
Pawns cannot be left unpromoted but Frogs can - and must if moving within the far rank.

Check, Checkmate, and Stalemate are as in FIDE Chess.

Notes

I ruled out Pawn promotion to simple pieces as it would be a complication to also allowing Frogs to be promoted, and I didn't feel like laying the variant open to debating the relative strength of the colourbound Bishop, colourswitching Knight, and Frog which is neither!

The rhyme Humpty Dumpty describes how the cannon so named met its demise in the siege. No doubt illustrations would have depicted the cannon in a more animate form with an open-mouthed face - like the "barking dog" cannons in Terry Pratchett's Interesting Times. The next stage must have been a loss of perspective, taking out the depth of the fortifying wall and length of the cannon. So the sense of "wall" as fortification and Humpty as cannon became forgotten, reducing the character to a spheroidal monster perched precariously on a narrow garden wall.