Prisoner's Escape

Peter Aronson

Introduction

Prisoner's Escape was inspired by Ralph Betza's proposed game of Anticheckmate Chess, where the White and Black Kings are switched, and the first player whose King ends the turn unattacked wins. It differs from Anticheckmate Chess in that: ending the turn with the your King unattacked is check for your opponent, not a win, and your opponent must end their turn with your King unattacked for a win (mate); the pieces are for the most part non-standard, and it is played on a board of 44 squares instead of a standard Chess board.

General Rules

The rules of Prisoner's Escape are generally identical to those of FIDE Chess, except where noted otherwise below.

The largest difference is Prisoner's Escape concept of check and checkmate. A player is in check when at the start of their turn, the opposing Prisoner is not attacked. It is checkmate if they are not able to move so that at the end of their turn the opposing Prisoner is attacked. Following usual FIDE Chess rules, when in check, only moves that relieve check are legal. Stalemate is possible, if unlikely, and is a draw as in FIDE Chess.

Board and Setup

Prisoner's Escape is played on a board of 44 squares with 13 pieces to a side.

+---+ 8 |:I:| +---+---+---+---+---+---+---+ 7 |:f:| n |:h:| g |:h:| n |:f:| +---+---+---+---+---+---+---+ 6 | p |:p:| p |:p:| p |:p:| p | +---+---+---+---+---+---+---+ 5 |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+ 4 | |:::| |:::| |:::| | +---+---+---+---+---+---+---+ 3 |:P:| P |:P:| P |:P:| P |:P:| +---+---+---+---+---+---+---+ 2 | F |:N:| H |:G:| H |:N:| F | +---+---+---+---+---+---+---+ 1 | i | +---+ a b c d e f g

White: Prisoner (I): d8; Guard (G): d1; Falcons (F): a2 g2; Hunters (B): c2 e2; Knights (N): b2 g2; Pawns (P): a3 b3 c3 d3 e3 f3 g3

Black

Prisoner (I): d1

Guard (G): d7

Falcons (F): a7 g7

Hunters (B): c7 e7

Knights (N): b7 g7

Pawns (P): a6 b6 c6 d6 e6 f6 g6

The Moves of Pieces

The Prisoner moves one step in any direction (like a King), but may not capture.
Pawns move and capture like FIDE Pawns, but have no initial double move or en-passant capture. Upon reach the rank upon which the opposing non-Pawn pieces started, they promote to the ownering player's choice of Guard, Hunter, Falcon or Knight.

The following pieces -- the Knight, Hunter, Falcon and Guard -- have in addition to their normal moves, the ability to make a friendly leap forward or diagonally forward. For a friendly leap to be made, a friendly piece must be adjacent to the leaping piece, in one of the three forward squares, and the space immeadiately beyond the friendly piece in the same direction must be empty. The leaping piece may then leap over the friendly piece to that empty square. The following diagram shows the possible friendly leaps for the White Guard on the first turn:

+---+ 8 |:I:| +---+---+---+---+---+---+---+ 7 |:f:| n |:h:| g |:h:| n |:f:| +---+---+---+---+---+---+---+ 6 | p |:p:| p |:p:| p |:p:| p | +---+---+---+---+---+---+---+ 5 |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+ 4 | |:*:| |:*:| |:*:| | +---+---+---+---+---+---+---+ 3 |:P:| P |:P:| P |:P:| P |:P:| +---+---+---+---+---+---+---+ 2 | F |:N:| H |:G:| H |:N:| F | +---+---+---+---+---+---+---+ 1 | i | +---+ a b c d e f g

Where the green circles/'*'s show where the Guard can leap to.

The Knight moves just like the FIDE Knight, which is to say, any square two squares away that could not be reached by a Queen (or more formally: "The knight may move to one of the squares nearest to that on which it stands but not on the same rank, file or diagonal"). Thus, a Knight on d1 could move to f2.

The Falcon comes from Hunter Falcon Chess, invented by Karl Schultz in 1943. It moves forward as a Bishop, and backwards as a Rook.

+---+ 8 |:::| +---+---+---+---+---+---+---+ 7 |:*:| |:::| |:::| |:*:| +---+---+---+---+---+---+---+ 6 | |:*:| |:::| |:*:| | +---+---+---+---+---+---+---+ 5 |:::| |:*:| |:*:| |:::| +---+---+---+---+---+---+---+ 4 | |:::| |:F:| |:::| | +---+---+---+---+---+---+---+ 3 |:::| |:::| * |:::| |:::| +---+---+---+---+---+---+---+ 2 | |:::| |:*:| |:::| | +---+---+---+---+---+---+---+ 1 | * | +---+ a b c d e f g

(This piece is not to be confused with the Falcon from Falcon Chess, which would be distinctly crowded on a board this side.)

The Hunter also comes from Hunter Falcon Chess. It moves forward as a Rook, and backwards as a Bishop.

+---+ 8 |:*:| +---+---+---+---+---+---+---+ 7 |:::| |:::| * |:::| |:::| +---+---+---+---+---+---+---+ 6 | |:::| |:*:| |:::| | +---+---+---+---+---+---+---+ 5 |:::| |:::| * |:::| |:::| +---+---+---+---+---+---+---+ 4 | |:::| |:H:| |:::| | +---+---+---+---+---+---+---+ 3 |:::| |:*:| |:*:| |:::| +---+---+---+---+---+---+---+ 2 | |:*:| |:::| |:*:| | +---+---+---+---+---+---+---+ 1 | | +---+ a b c d e f g

The Guard combines the moves of the Hunter and Falcon, move forward or backward like a Rook or a Bishop. The Guard lacks any side-to-side moves.

+---+ 8 |:*:| +---+---+---+---+---+---+---+ 7 |:*:| |:::| * |:::| |:*:| +---+---+---+---+---+---+---+ 6 | |:*:| |:*:| |:*:| | +---+---+---+---+---+---+---+ 5 |:::| |:*:| * |:*:| |:::| +---+---+---+---+---+---+---+ 4 | |:::| |:G:| |:::| | +---+---+---+---+---+---+---+ 3 |:::| |:*:| * |:*:| |:::| +---+---+---+---+---+---+---+ 2 | |:*:| |:*:| |:*:| | +---+---+---+---+---+---+---+ 1 | * | +---+ a b c d e f g

Notes and Comments

Like a lot of my contest games, this game started as board. Looking at the board, I wondered what you could play on it. At some point it occured to me that King's Escape, my slight variant on Ralph's Anticheckmate Chess would fit nicely, with the King in the "cell" at the top and the bottom, and the standard array minus the King on the second and seventh rows. However, it turned out that with that much power on the board, it was really hard to ever check your opponent, so weaker pieces seemed to be called for. I had already thought about using the Hunter Falcon Chess pieces -- their lack of sideways moves and lack of colorboundness seemed to fit what I was looking for. However, development was a pain, so I added the friendly leap.

As I mentioned above, stalemate is possible in this game. Here's an example with White to move:

+---+ 8 |:I:| +---+---+---+---+---+---+---+ 7 |:::| |:h:| g |:h:| |:::| +---+---+---+---+---+---+---+ 6 | |:::| |:::| |:::| | +---+---+---+---+---+---+---+ 5 |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+ 4 | |:::| |:::| |:::| | +---+---+---+---+---+---+---+ 3 |:i:| |:::| |:::| |:::| +---+---+---+---+---+---+---+ 2 | |:::| N |:::| |:::| | +---+---+---+---+---+---+---+ 1 | | +---+ a b c d e f g

Computer Play

I've written an implementation of Prisoner's Escape for Zillions of Games. You can download it here:

prisoners-escape.zip

The ZIP archive also includes a ZRF for King's Escape, which is close to Ralph's Anticheckmate Chess, but uses the Prisoner's Escape checkmate rules instead of Anticheckmate's instant win.

Written by Peter Aronson.

WWW page created: December 19th, 2003.

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Created on: March 27, 2004. Last modified on: March 27, 2004.