Object: Checkmate the opponent's King.
 
Some or all pieces are treated as transparent. When a piece is transparent, then a Rook, Bishop or Queen can go right through it and land on any empty square behind it.
 
Variant 1: All pieces are transparent.
Variant 2: Only friendly pieces are transparent.
Variant 3: Only enemy pieces are transparent.
 
Apart from this, all standard chess rules apply.
 
 
For more freeware as well as real puzzles and games see my home page http://karl.kiwi.gen.nz.