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Rule Zero is a collection of ground rules that are written by Ralph Betza. Within the context of this site's chess variants, Rule Zero is identical to this reference version. I shall reproduce the rules here later.

## Rule Zero of Rule ZeroEdit

All rules of FIDE Chess apply unless overridden by the following rules.

## CastlingEdit

Castling is a way to make a game faster, by putting the big fighter pieces nearer to the action and the Royal piece

Strict castling always places the royal piece on the square that is the mean/midpoint of the two piece's coordinates. Any halves are rounded away from the center of the board.

For example, on this board: (K = FIDE King, R = FIDE Rook)

+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| R |   |   |   |   |   |   |   |   |   | K |   |   |   |   |   |   |   |   | R | 1
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t


Castling with the a-side rook would result in the King being placed $\frac{11 + 1}{2} = 6$ squares in, i.e. f1. Thus, the King is placed on f1, and the Rook at g1.

Likewise, castling with the t-Rook creates would result in the King being placed $\frac{11 + 20}{2} = 15.5$ squares in. This is rounded away from the center to 16 – p1 – and the Rook placed on o1.

With colorbound pieces, though, there is still one more step to take.

Let's replace the FIDE Rooks in the above diagram with HHs.

+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| H |   |   | ^ |   |   | ^ |   |   | ^ | K |   |   | * |   |   | * |   |   | H | 1
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t


In the above diagrams, the squares marked with a ^ represents which squares the a-HH* can leap to up to the midline, and * likewise for the t-HH*. Castling a-side is nothing special: as g1 is reachable by the a-side HH*, it acts much the same way as with the Rook.

However, o1 is not a square that the t-HH* may reach. Thus, when the King is moved to p1 and the HH moved to o1, the entire system is shifted to the nearest square that the t-HH* can reach. In this case, the two are moved one square left, so the King moves to o1 and the t-HH* to n1.

## Oblique piecesEdit

Oblique, or hippogonal pieces, are understood to move orthogonally first, then diagonally to the destination.

For a (3, 5) leaper: (0, 0) → (0, 1) → (0, 2) → (1, 3) → (2, 4) → (3, 5)

For a (5, 8) leaper: (0, 0) → (0, 1) → (0, 2) → (0, 3) → (1, 4) → (2, 5) → (3, 6) → (4, 7) → (5, 8)

For a (2, 3, 4) leaper: (0, 0, 0) → (0, 0, 1) → (0, 1, 2) → (1, 2, 3) → (2, 3, 4)

If the oblique piece is declared non-jumping, then it cannot move to the destination if any piece in its path is blocked.

## PawnsEdit

Pawns can be promoted to any piece that was ever on the board in the game upon reaching the final rank or the eighth rank, whichever is closer.

If the board is longer than eight ranks long, any FIDE-like pawn (i.e. mfWcfF) may make arbitrarily long steps to the midline of the board, rounded towards the player.

## Object and King PlacementEdit

If the object is King Capture, then you may put your King in check, and will be obligated to do so if it is the only available move.

If the object is King Checkmate, then you may not put your King in check. If no other moves are available, this will be treated as stalemate.

If stalemate is the object, there are no royal pieces, and repetition will have special status. See below.

Unless otherwise stated, if one has multiple royal pieces only one needs to be retained.

## Board situation repetitionEdit

Repeating the same board situation three times in ten turns is considered a weak loss by the player starting the repetition. If there is no such thing as a weak loss, then a draw is used.

The exception is when stalemate is the object. If stalemate is the object then the player starting the repetition loses immediately.