Place the given number of queens into the grid so that none of them stands on a number and each number equals to the number of directions from which the given square is attacked by a queen. A queen attacks to arbitrary distance horizontally, vertically and diagonally. Queens block other queens.
(Rules (modified) and example (5 queens) from WPC 2005 IB)
- Most popularly the goal is to place given number of queens, but this puzzle works with any set of chess pieces.
History of the puzzle
The name of this article is based on a puzzle from WPC 2005/Part 11, "Innovative" round.
However, a version of this puzzle that uses 5 different chess pieces appeared on December 1995 issue of GAMES magazine. Author of the puzzle was Rodolfo Kurchan (Argentina).
Original title "Amenaza fantasma" was can be translated to "Ghost Threat". This name coincides with the Spanish title for the film Star Wars: Episode I - The Phantom Menace, but the film was released in 1999.