Jungle (Dou Shou Qi)

Jungle is a two-player game on a 7-column by 9-row board. Coordinates are written [col, row], with columns 0..6 from left to right and rows 0..8 from bottom to top. Seat 0 starts at the bottom and moves first; seat 1 starts at the top.

Board

Each player has one den. Seat 0's den is [3,0]; seat 1's den is [3,8]. Each den has three adjacent traps. Seat 0's traps are [2,0], [4,0], and [3,1]. Seat 1's traps are [2,8], [4,8], and [3,7].

The river consists of the 12 squares whose columns are 1, 2, 4, or 5 and whose rows are 3, 4, or 5. Every other square is land.

Pieces

Each side has one piece of each kind. From weakest to strongest, the ranks are:

rat (1), cat (2), dog (3), wolf (4), leopard (5), tiger (6), lion (7), and elephant (8).

Movement

An action has the form {from:[c,r], to:[c,r]}. A normal move goes one square orthogonally. A piece cannot leave the board, enter its own den, or move onto a friendly piece. Only rats may enter river squares. Rats may move from the river back onto land.

Lions and tigers may jump across the river. A horizontal jump crosses exactly two river squares, from one bank to the opposite bank (for example [0,r] to [3,r] or [3,r] to [6,r], where r is 3, 4, or 5). A vertical jump crosses exactly three river squares, for example [c,2] to [c,6] for c equal to 1, 2, 4, or 5. Every river square crossed must be empty. Any rat, from either side, blocks a jump. The landing square may be empty or contain an enemy piece, but may not contain a friendly piece.

Capturing

A piece may capture an enemy piece of equal or lower rank. A rat may capture an elephant; an elephant may not capture a rat. A piece in the opponent's trap has effective rank 0, so any enemy piece may capture it. A piece in its own trap keeps its normal rank.

A rat in the river can capture only an opposing rat that is also in the river, and can be captured only by such a river rat. Land pieces, including a land rat, cannot capture a river rat or be captured by one. A river rat cannot capture a land piece. A land rat can capture a land elephant normally.

Captures remove the captured piece from the board. Moving into an enemy den wins the game for the moving side. Capturing all opposing pieces also wins.

Draws and no moves

If the side whose turn begins has no legal move, that side loses. The game is drawn when 400 plies have been played, or when 100 consecutive plies have passed without a capture. These limits may be configured by the engine. A ply is one move by one side; a capture resets the no-capture counter.

After a win or draw, neither side has an active turn.