Fault Line

Introduction

Fault Line is an entry for 40-Squares Chess Variant Contest. The gimmick of sliding ranks is also present in board games like Variance and Shuttles. Fault Line also bears some resemblance to the Aftershock variant of Earthquake Chess.

Setup

The board has six ranks. Ranks 2 and 5 have six squares while ranks 1, 3, 4, and 6 have seven squares. The six ranks should be made from six individual planks so they can slide freely.

The starting positions are shown in the diagrams below. It is best if the board were not checkered, but for illustration purposes, a checkered board is shown in the graphic version.

Graphic Version:

ASCII Version:

      a   b   c   d   e   f   g   h    
        +---+---+---+---+---+---+---+     White:
  6     | r | n | b | k | b | n | r | 6     Rook   : a1 & g1
        +---+---+---+---+---+---+---+       Knight : b1 & f1
  5     | p | p | p | p | p | p |     5     Bishop : c1 & e1
        +---+---+---+---+---+---+---+       King   : d1
  4     |   |   |   |   |   |   |   | 4     Pawn   : b2, c2, d2, e2, f2 & g2
    +---+---+---+---+---+---+---+---+  
  3 |   |   |   |   |   |   |   |     3   Black:
    +---+---+---+---+---+---+---+           Rook   : b6 & h6
  2     | P | P | P | P | P | P |     2     Knight : c6 & g6
    +---+---+---+---+---+---+---+           Bishop : d6 & f6
  1 | R | N | B | K | B | N | R |     1     King   : e6
    +---+---+---+---+---+---+---+           Pawn   : b5, c5, d5, e5, f5 & g5
      a   b   c   d   e   f   g   h    

Object

The goal is to either capture the opposing king or move your king to the far side of the board (rank 1 for black, rank 6 for white). The first player to accomplish either goal wins. Apply the usual rules for stalemates by repetition, etc.

Movement

During your turn, you may either move a piece or slide a rank. Rules for movement and capture are per normal chess with the following exceptions and clarifications.

Pawns

Pawns may not make an initial double-move and thus there is no pawn capture en passant (pretty standard for small chess variants).

When a pawn reaches the far end of the board (rank 6 for white, rank 1 for black), it must promote to a rook, bishop, knight, or queen.

Bishops

By sliding ranks, each bishop has access to the entire board.

Castling

The king moves two spaces toward the castling rook. The corresponding rook moves two spaces to the other side of the king. The requirements and restrictions on castling are per normal chess. Sliding the king's rank does not negate the possibility of castling.

Missing Spaces

Pieces cannot occupy or move past missing spaces, such as a2 and h5. Missing spaces do not block diagonal movement. Knights leap over missing spaces.

Examples: A rook could never move from a1 to a3 because there is never a space at a2. A bishop could move from a1 to b2 and a knight could jump from b1 to a3, assuming neither destination square was occupied by a friendly piece.

Sliding Ranks

You control a rank if the majority of pieces on the rank are yours. If both players have an equal number of pieces on the rank, the rank is uncontrolled.

If you wish to slide an uncontrolled rank, you must first ask your opponent's permission. If granted, you must then slide the rank. If denied, you may not slide the rank that turn, but you may ask again on subsequent turns. You do not need permission to slide a rank you control. You may not slide a rank your opponent controls.

Ranks slide one space to the left or right. The board can never extend past files a or h. Each rank has only one direction in which it may slide; once it slides, a rank can only slide again in the opposite direction. Ranks 2 and 5 are fixed and cannot slide.

Example: From the starting position, white could slide rank 1 one space to the white's right.

      a   b   c   d   e   f   g   h    
        +---+---+---+---+---+---+---+  
  6     | r | n | b | k | b | n | r | 6
        +---+---+---+---+---+---+---+  
  5     | p | p | p | p | p | p |     5
        +---+---+---+---+---+---+---+  
  4     |   |   |   |   |   |   |   | 4
    +---+---+---+---+---+---+---+---+  
  3 |   |   |   |   |   |   |   |     3
    +---+---+---+---+---+---+---+      
  2     | P | P | P | P | P | P |     2
        +---+---+---+---+---+---+---+  
  1     | R | N | B | K | B | N | R | 1
        +---+---+---+---+---+---+---+  
      a   b   c   d   e   f   g   h