; Wurzburg-Plachutta. ; ; $pieceA and $pieceB each move to a critical square. ; each also has a unique square it must have access to for defense ; each, in separate variations, occupies the critical square, creating ; a Holzhausen interference which white exploits, so that ; each interferes with the other's ability ; to access the square it needs. cql(input heijden.pgn variations result 1-0 ) mainline piece $pieceA in [qrb] piece $pieceB in [qrb] not $pieceA on $pieceB ;exclude identity square $criticalsquare in attack($pieceA _) on attack ($pieceB _) ; the critical square is attacked by both thematic pieces not $criticalsquare on between ($pieceA $pieceB) ; exclude unthematic cases where pieces are on the same line btm next ( btm ; the move to the critical square by pieceA {wtm $pieceA on $criticalsquare} {btm ray ($pieceB $pieceA move from $pieceA) ;pieceA hides its target from pieceB } ) next ( btm ; pieceB move to the critical square {wtm $pieceB on $criticalsquare} {btm ray ($pieceA $pieceB move from $pieceB) } )