Joust Chess

Joust Chess is a variant based on the theme of rotating pieces, inspired by Ploy, Rotary, and Tournoy, with the design goal that all pieces but the king follow a consistent set of rules, differentiated only by the pattern of directions available to each piece.

Setup

Pieces

   'Pawn': These have two directions (hereafter 'pips' for brevity) 180° apart. As a consequence of the rules (see below, likewise for all other pieces), the pawns are generally incapable of long-range captures, and serve the primary purpose of defending or obstructing specific squares. Each player has 8 pawns filling either the 2nd or 7th rank, with pips initially pointing forward.

   'Wedge': These have two pips at a 90° angle. This allows long-range capturing by making a long-range move in one direction followed by an adjacent capture in the other direction. It also allows short-range double-captures. Each Player has 4 of these. 2 adjacent to the king and queen, with the pips initially in the two diagonally forward directions, and 2 in the corners, with one pip directly forward and the other toward the center of the board.

   'Hook': These have 3 pips in a T pattern, enabling long-range double-captures and short-range triple-captures. Each player has 2, one adjacent to each corner, with the central pip directed diagonally forward and away from the center of the board.

           'Queen': These have 4 pips in a cross pattern, eliminating the Hook's blind spot. Each player has 1 adjacent to the king, with the pips initially in the orthogonal directions.

           'King': Same as the Queen, but restricted to short-range movement, and of course the loss of the king means the loss of the game.

Rules

As in traditional chess, the goal is to checkmate the opponent's king, with 'check' defined by a piece's normal capturing capabilities. Alternatively, the goal may be to capture the opponent's king. There is little difference, as it is always possible to make a legal move, since one may simply rotate a piece in place.

All pieces but the king follow the same rules and are distinguished only by their available pips, and even the king follows nearly the same rules. On each turn, the player to move selects a piece and performs one or more actions with that piece. Multiple actions may be performed with a single piece on a single turn as long as the criteria for each action are met. Each individual action is optional, but the player must perform at least one action on his or her turn. The actions available to a piece are as follows.

1. A piece may move without capturing, any number of squares in the direction of any available pip, as long as no other piece obstructs the movement. This may only be done as the first action on a given turn.

2. A piece may jump over an adjacent piece of the same color, landing on the unoccupied space behind it, in the opposite direction of any available pip that has not been used during the turn. This may not be done if any captures have been performed during the turn.

3. A piece may capture an adjacent enemy piece by replacement, in the direction of any available pip that has not been used during the turn.

4. A piece may rotate to a new orientation if it meets at least one of the following criteria:
a. No captures have been performed during the turn.
b. Every available pip has been used during the turn.
Rotation may only be performed as the final action of the turn. A valid orientation is one in which all pips are pointed in one of the 8 standard queen-like directions. A rotation which leaves the same combination of directions available to the piece is not a valid action (example, rotating the pawn 180°).

Again, all pieces but the king follow the same rules, and are distinguished only by their available pips. The only difference with the king is that action 1, moving without capturing, is limited to a single step rather than sliding as far as desired. However, through jumps or captures, it's not uncommon for the king to be able to move more than one square in a single turn. If the king passes through check, that is permissible, as long as he is not in check at the end of the turn.

In particular, note that there is no inherent restriction to how many jumps or captures can be performed in a turn, as long as no pip is used twice. Note though that non-capturing movement can only be done once per turn, since it can only be done as the first action. Likewise rotation can only be done once per turn, since it can only be done as the last action.

Notes

Since a long-range capture is performed by making a long-range move with one pip, followed by an adjacent capture with a different pip, pawns are incapable of long-range captures. The enemy piece would have to be back in the direction the pawn just came from. The only way a pawn can capture from more than 1 square away is to use one pip to leap over a friendly piece, then use the other pip to capture an enemy piece one more step in the same direction (since jumps are performed using the pip in the opposite direction of the jump).

Since it is always legal to rotate your king in place if he's not in check, stalemate is impossible.

A king and wedge (or any other back-row piece) can force checkmate against a lone king. See the diagram below for an example of the white king and wedge preparing to checkmate the black king.

In the diagram, the 'X's mark the squares threatened by the wedge, fencing in the black king. The white king is positioned to use his bottom-left pip to leap over the wedge, then use the top-right pip to capture the black king. So the black king is currently in check, and must move up or to the right. Either way, white can respond by moving the wedge one square in the same direction, shrinking the area of the board into which the black king is trapped. Any time the black king is not in the corner of the fenced-in area, the wedge can move to shrink it. If the black king sits in the corner of the fenced-in area and just rotates in place, the white king can set up another check like the one shown and thus force the black king to move. Eventually the black king is trapped in the corner of the board and the white king can deliver checkmate.

Because of how long-range captures are performed, it's possible for one piece to obstruct another without being in danger. This is crucial to the tactics of the game.

Although there is no castling, if the back row has been partially emptied, the ability to jump over friendly pieces still makes it possible to quickly tuck the king into the corner for safety.

This submission is posted by the inventor.

Last revised by Jeff Cornell.