# wurzburg-plachutta.cql

// Download wurzburg-plachutta.cql// PGN output when run on sample.pgn

/************* Wurzburg-Plachutta. Two pieces, X and Y, 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. Note that "ray (X Y .)" is the set of squares Z such that there is a ray from X to Y to Z *************/ cql(input hhdbvi.pgn variations result 1-0 ) mainline btm piece X in [qrb] piece Y in [qrb] & ~X square CriticalSquare in (_ attackedby X) & (_ attackedby Y){ // the critical square is attacked by both thematic pieces not CriticalSquare in between (X Y) // exclude unthematic cases where pieces are on the same line line --> move from X to CriticalSquare --> wtm --> ray (Y X move to . from X) line --> move from Y to CriticalSquare --> wtm --> ray (X Y move to . from Y) }