Community variant

Doppelganger

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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: king (k), custom piece 3 (q), rook (r), custom piece 2 (b), custom piece 1 (n) and pawn (p).
custom piece 1 (n) is a custom piece with Betza movement `mNcB`.
custom piece 2 (b) is a custom piece with Betza movement `mBcN`.
custom piece 3 (q) is a custom piece with Betza movement `mQcK`.
The royal piece king (k) uses custom Betza movement `mKcQ`.

Move rules

Castling is allowed.

Promotion

The pieces that can promote are: pawn (p).
Promotion choices are both sides: custom piece 1 (n), custom piece 2 (b), rook (r) and custom piece 3 (q).

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 (N) movement

mNcB

Custom piece 2 (B) movement

mBcN

Custom piece 3 (Q) movement

mQcK

Custom king (K) movement

mKcQ

move capture move or capture initial only hopper target

Fairy-Stockfish rules

[doppelganger:chess]
variantTemplate = chess

# 1. Castling remains fully enabled
castling = true

# 2. Custom normal pieces
# Knight: Moves like a Knight (mN), Captures like a Bishop (cB)
customPiece1 = n:mNcB

# Bishop: Moves like a Bishop (mB), Captures like a Knight (cN)
customPiece2 = b:mBcN

# Queen: Moves like a Queen (mQ), Captures like a King (cK)
customPiece3 = q:mQcK

# 3. The Custom King! 
# By using the specific "king =" parameter instead of "customPiece", 
# the engine applies the custom moves but KEEPS the hardcoded castling rules.
king = k:mKcQ

# 4. Promotion Configuration
# Only pawns can promote, and they can choose any piece except the King
promotionPawnTypes = p
promotionPieceTypes = n b r q

# 5. Standard Board Setup
startFen = rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1