King's Run

by Fergus Duniho

for "The 32-Turn Challenge"

Concept

King's Run is inspired by the movie Logan's Run and is intended as an entry into the 32 turn contest. In the movie, people lived in a domed city, isolated from the outside world, where everyone who reached the age of 30 had to voluntarily commit suicide or be hunted down. Those who tried to escape were called Runners, and it was the job of Sandmen to terminate them before they escaped. Logan was a Sandman who became a Runner, at the young age of 26, when the computer who ran the place gave him a mission to find Sanctuary, the place all the Runners ran to, and destroy it. Instead of carrying out his mission, Logan escaped from the city. For those who haven't seen the movie, I won't spoil it for you here. It's an excellent movie. Go rent it or check it out of the library.

The basic thought which led to the creation of this game is that people in Logan's Run weren't allowed to live beyond the age of 30, and games in the 32-turn contest may last no longer than 32 turns. So I thought about designing a game for the contest which is based on Logan's Run. As it happens, elements from Logan's Run work well with a Chess game which must last no more than 32 turns. In Logan's Run, a person first turns 30, then commits suicide or gets killed by a Sandman. This is a two-step process. If each of a player's 16 pieces each go through a similar two-step process, that is 32 turns.

Another idea borrowed from Logan's Run is the goal of escaping. So one way for you to win is to move your King off the board. How to do this is described in the rules. The name of the game refers to the King's attempt to escape the board.

Pieces

King's Run uses two sets of pieces. These should be different in design, size, or color. One set is to represent the Sandman pieces, and the other set is to represent Runner pieces. All pieces begin as Sandmen, and during the course of the game, Sandmen become Runners. Unless a player can make a move that will immediately win the game, a Sandman piece must capture a Runner piece of the same color whenever such a capture is possible.

The Runner King has one special move unavailable in Chess. When it is on the last rank, it can move off the board, thereby winning the game. Castling is unaffected by whether the King and Rook are Sandmen, Runners, or one of each. Because there is no checkmate in this game, it is legal to castle in and through 'check.'

QuickPawns replace Pawns, and the orthodox chess pieces are otherwise used for this game. QuickPawns may move forward 1 or 2 spaces on any turn, and they capture by moving one space diagonally forward. They may not capture each other by en passant. As far as I can tell, QuickPawns were introduced by Kevin Begley in Mammoth Chess.

Setup

At the start of the game, all pieces are Sandmen. Eight QuickPawns fill up the second rank, as Pawns normally do in Chess, and the other pieces begin where they do in Chess. Each player also begins with one chip held in hand.

Rules

King's Run is played like regular Chess with the following exceptions:

1. Win, Loss, and Draw Conditions
   1. A player loses if his King is captured.
   2. A player wins by moving his King off the board
      1. A King may move off the board if it is a Runner and on the last rank.
   3. The game ends in a draw if each player is reduced to a bare Runner King with no chips left.
2. Each player begins the game with a poker chip, which is held in hand.
3. Each turn consists of two parts.
   1. First, the player moves a piece.
      1. If a player can make a winning move, he must do so.
      2. Otherwise, if he can capture one of his Runner pieces with one of his Sandman pieces, he must do so.
         1. This sometimes means that a player must capture his own King, thereby losing.
      3. Otherwise, a player can make any orthodox chess move.
   2. The player ends his turn by doing one of the following:
      1. Turns one of his Sandman pieces into a Runner.
      2. Removes one of his non-royal Runner pieces from the game.
      3. Discards a chip held in hand.
4. Whenever a piece is captured (as opposed to merely being removed), the player whose piece is captured gets two chips for a captured Sandman and one for a captured Runner.
   1. If a player gets a chip for capturing one of his own Runners, it is available for immediate use on the second part of his turn, or it may be saved for later use.

Game Length

This game can last no more than 32 turns. A player can turn a maximum of 16 pieces into Runners, remove a maximum of 15 pieces, and if a player loses all non-royal pieces by removing them as Runners, he can pass on one of these only once. This gives a player a maximum of 32 turns, for 16+15+1=32.

Each time a Sandman piece is captured, a player loses the opportunity to turn it into a Runner and remove it on subsequent turns. This would normally reduce the number of available turns by two. This is compensated for by giving the player two additional chips. If a player lost all his non-royal pieces before they become Runners (which is actually impossible), his turns would be limited to turning one piece (the King) into a Runner and discarding 31 poker chips. This gives a player a maximum of 32 turns, for 1+31=32.

Each time a Runner is captured, it prevents a player from removing that piece on the second part of his turn. This would normally reduce the number of available turns by one. This is compensated for by giving the player an additional chip. If a player's pieces all become Runners and were all lost by being captured, his turns would be limited to turning a maximum of 16 pieces into fugitives and discarding a maximum of 16 chips (one for each of the 15 captured non-royal pieces plus the original one each player starts with). This gives a player a maximum of 32 turns, for 16+16=32.

Any combination of these possibilities will also be limited to 32 turns.

Design Considerations

The first design consideration was to design a game which would last no longer than 32 turns, as this is the condition of the 32-turn contest. There are various ways to do this. My other entry, Wormhole Chess, does this by removing spaces from the board. This one does it by removing pieces.

Another consideration was to allow the game to last the full 32 turns available to it, as that will make the game more interesting. Since each side has only 16 pieces, piece attrition takes two steps, for a total of 32 turns. But the King is never removed, which leaves only 31 turns, and captures could speed up piece attrition, causing the game to end earlier. The use of chips is added to let the game use the full 32 turns.

In implementing the game for Zillions, I discovered that en passant could not be implemented properly. I also realized that en passant was originally added to Chess as a solution for a problem which is inconsequential in this game. En passant was introduced into regular Chess to help Pawns move past enemy Pawns that are blocking them. This is less of a problem in this game, because pieces are regularly being eliminated from the game, and Pawns are often the first to go. So I eliminated en passant.

Thinking about this also led to another insight. Pawns would rarely reach the last rank in a game limited to 32 turns by piece attrition, especially considering that players will normally prefer to get rid of their Pawns before they get rid of more powerful pieces. So I replaced Pawns with QuickPawns, which have a better chance of reaching the last rank and promoting before the game ends.

Since it can sometimes be hard to checkmate with ever dwindling forces in a game limited to 32 turns, and since the game is based on Logan's Run, I added another win-condition, one which is based on what Logan is after in Logan's Run. A player can win by moving his King off the board, which is analogous to Logan escaping the domed city he lived in.

I also considered whether to allow forced moves which take priority over moving a King out of danger. I decided to leave them in the game, because they make stalemate less likely. This helps counteract the tendency this game otherwise has toward stalemate positions, which can easily happen toward the end of the game, when both sides lose adequate mating material before they can make good use of it.

Zillions of Games

I developed this game with the help of Zillions of Games, and you may download a ZRF file for playing King's Run with Zillions of Games:

• kingsrun.zip

In the Zillions implementation, I used abstract pieces for the Sandmen pieces, and I used magnetic pieces for Runners. On the second part of your turn, picking a piece up and dropping it back down will change a Sandman into a Runner, remove a Runner from the board, or discard a chip. Only some of the chips held in hand may be discarded in this implementation. This is merely to reduce the number of alternative moves Zillions has to calculate.

Because move-types cannot be nested in Zillions, and because move-types had to be used for both move-priorities and turn-order, the moves available on the second part of the turn are technically available on the first part, but they have the lowest priority, and a player should always be able to make a higher priority move. So this shouldn't cause Zillions to part from the official rules of the game.

I think the draw condition was implemented imperfectly. It draws when Black has only one piece left, which should normally be when both sides are down to one Runner King with no chips left. But if Black waited until the very end to turn his King into a Runner, the draw condition, as implemented, would occur prematurely. This is a rare circumstance and will probably have little effect on the course of the game when it does happen.