Fusion Chess Rules:
- Standard chess rules apply (checkmate, stalemate, castling, en passant, pawn promotion, threefold repetition).
- Special Rule - Piece Combining: When a non-king, non-pawn piece captures an enemy non-king, non-pawn piece, they combine into one piece.
- Combining Restrictions:
- Kings and pawns never combine.
- Same-type pieces cannot combine (e.g., Rook captures Rook = normal capture, no combining).
- Only two pieces can be combined at a time (no triple combinations).
- Pieces only combine with opponent pieces, never your own.
- Combined Piece Movement: A combined piece can move like either of its two component pieces.
- When a Combined Piece Captures:
- Captures a non-combined piece: If the captured piece type matches the primary OR secondary type of the combined piece, it's a normal capture (no recombining). Otherwise, the secondary piece is replaced with the captured piece type.
- Example: Rook+Bishop captures Knight → becomes Rook+Knight (Bishop replaced).
- Example: Rook+Bishop captures Rook → stays Rook+Bishop (normal capture, no change).
- Captures a combined piece: Normal capture, the attacker remains unchanged.
- When a Non-Combined Piece Captures a Combined Piece:
- The attacker becomes the new primary piece.
- The target's primary piece becomes the new secondary piece.
- The target's secondary piece is discarded (captured).
- Example: Knight captures Bishop+Rook → becomes Knight+Bishop (Rook is discarded).
- Special Cases:
- Pawn promotion takes precedence when a pawn reaches the opposite rank.
- En passant captures work normally but do not result in combining (pawns don't combine).
- Promoted pieces (e.g., promoted Queens) can combine normally after promotion.
Visual Indicators: Combined pieces show a small secondary piece icon in the top-right corner and a red "+" badge.