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# Conversion Chess

Conversion chess has been invented in 1973 by Ralph Betza.

### Rules

The standard rules of co-Chess apply, except where explicitly stated as otherwise so.

The standard rules of Co-chess are:

1. The standard rules of chess apply except where stated.
2. In co-chess, each pair of identical pieces of the same colour (excluding pawns) forms a co-pair.
Kings also form co-pairs with queens.
Promoted pieces allow multipairing.
3. Whenever one member of a co-pair moves to a square not on the same rank or file as the other, the co-pair defines two co-squares, each on the same rank as one of the pieces and the same file as the other.
Only a moving piece can form co-squares.
Castling is both a king move and a rook move, so both pieces can form co-squares thereby.
4. Any piece on a co-square is subject to a co-effect.
The nature of the co-effect defines the game being played.
Co-effects are mandatory.
A square is only a single move a co-square: after the move that formed the co-square, the co-effect is carried out, but not after that (but a square could become co-square multiple times).
Pawn promotion cannot cause co-effects.
Castling into check is permitted if the check is removed by means of the co-effect.
1. The co-effect in conversion chess is conversion: any enemy piece on a co-square is converted to a friendly piece of the same type.
2. Friendly pieces are unaffected.
3. Conversion of a piece does not cause further conversion.
4. A threat to convert the King is check. This works exactly the same as regular check with respect to guarded squares, checkmate, and stalemate. Regular check exist too, of course.

### Sample games

Piero Pugnali - Alessandro Castelli (Grand Prix 1993) 0-1
1.Nf3?! d5 2.d4?? Bh3/Nf3+ 3.g:f3 Bg2/f2+ 4.Kd2 B:h1/Bf1 5.Q:f1/Pf2 Qd6 6.Q:h1 Qf4+ 7.Kd3 Qf5+ 8.Kc3 Nc6 9.e3 000+ 10.Resigns

Alessandro Castelli - Michele De Giglio (Grand Prix 1993) 1-0
1.e4 d6 2.d4 c6 3.Ag5 Qa5+?? 4.Ba6/Qa5 Resigns

Michele De Giglio - Alessandro Castelli (Grand Prix 1993) 0-1
1.e4 d5 2.c4 c6 3.c:d5 e5 4.Qh5/Pe5 Qa5/Pe5 5.Qg5+/Pe5 f6 6.e:f6 Kf7 7.f3?? Kg6/Qg5 8.Resigns