Community variant

Opposition

This is a user-catalogued casual variant. Technical details such as board size, FEN, pieces, and hand rules are defined in the Fairy-Stockfish variants.ini block below.

Uploaded by: Orca
Visibility: public
Status: active

Generated rule overview

This variant inherits its base rules from `chess` and overrides the settings shown below.

Board and setup

Default starting position

Pieces and movement

The piece set used on the board is: custom piece 1 (k), custom piece 6 (q), custom piece 5 (r), custom piece 4 (b), custom piece 3 (n) and custom piece 2 (p).
custom piece 1 (k) is a custom piece with Betza movement `K`.
custom piece 2 (p) is a custom piece with Betza movement `fmW,fcF,fm2W`.
custom piece 3 (n) is a custom piece with Betza movement `N`.
custom piece 4 (b) is a custom piece with Betza movement `B`.
custom piece 5 (r) is a custom piece with Betza movement `R`.
custom piece 6 (q) is a custom piece with Betza movement `Q`.

Move rules

Check restrictions are disabled; kings/royal pieces may be capturable depending on the variant goal.
Castling is not allowed.

Promotion

The pieces that can promote are: custom piece 2 (p).
Promotion choices are both sides: custom piece 6 (q), custom piece 5 (r), custom piece 4 (b) and custom piece 3 (n).

Capture effects

Some piece types cannot capture matching immune pieces.

Winning and losing

An extinction rule is active: reaching 0 remaining piece(s) k causes a loss for the side to move.

Piece movement

These diagrams show custom pieces and known Fairy-Stockfish built-in fairy pieces from White's perspective on a compact preview board. Some special moves, especially hoppers and game-state-dependent moves, can still depend on blockers or game state.

Custom piece 1 (K) movement

K

Custom piece 2 (P) movement

fmW,fcF,fm2W

Custom piece 3 (N) movement

N

Custom piece 4 (B) movement

B

Custom piece 5 (R) movement

R

Custom piece 6 (Q) movement

Q

move capture move or capture initial only hopper target

Fairy-Stockfish rules

[opp:chess]
variantTemplate = chess

# 1. Redefine the King (k) with standard King movement
customPiece1 = k:K

# 2. Redefine the Pawn with move-only, capture-only, and double-step rules
customPiece2 = p:fmW,fcF,fm2W

# 3. Redefine the rest of the standard pieces
customPiece3 = n:N
customPiece4 = b:B
customPiece5 = r:R
customPiece6 = q:Q

# 4. Corrected promotion rules
promotionPawnTypes = p
promotionPieceTypes = qrbn

# 5. Disable casting and standard check to bypass engine crashes
castling = false
checking = false

# 6. Set the King as the extinction target (capture to win)
extinctionPieceTypes = k
extinctionPieceCount = 0
extinctionValue = loss

# 7. Apply mutual immunity to all pieces except the King
mutuallyImmuneTypes = pnbrq

# 8. Standard starting FEN
startFen = rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1