David Pritchard, the author of "The Encyclopedia of Chess Variants", wrote that the "complexity and beauty" of losing chess is found in its endgame. He noted that, in contrast to regular chess, losing chess endgames with just two pieces require considerable skill to play correctly, whereas three- or four-pieces endgames can exceed human capacity to solve precisely. For example, the following endgames may turn out to be quite complicated: "2 Knights vs Rook", "3 Kings vs King", or "Bishop+Knight+King vs King". In the latter case, in particular, a win may require more than 60 moves, which means that it is sometimes unattainable due to the fifty-move rule.