Draw an arrow in each of the empty cells outside the main grid. Each arrow must point in one of the eight standard directions and must point to at least one numbered cell. Each numbered cell must be pointed at by exactly that number of arrows.
(Rules and example from PGP IB)
History of the puzzle
Invented by Masayuki Nagashima (Japan) in 1994. First appeared on December 1994 edition of the Puzzler magazine.
First appeared on WPC 2016/Round 11. The author of the puzzles was Ján Farkaš (Slovakia).
Put a number in each of the empty cells outside the main grid. Each number indicate the intensity of a lamp located in that cell. A lamp with 0 intensity is possible. A lamp of intensity N lits N cells in each of 8 directions. Each numbered cell must be lit by exactly that number of lamps.
(Example from WPC 2016 IB)
Appearances in the past WPCs
- WPC 2019/World Cup Round 1 by Roland Voigt
- WPC 2018/Round 2 by Jiří Hrdina
- WPC 2018/Round 13 (Coded) by Jiří Hrdina
- WPC 2017/Round 3 by Amit Sowani and Ashish Kumar
- WPC 2017/Round 10 ("Optimizer") by Amit Sowani
- WPC 2016/Round 9 by Matej Uher
- WPC 2016/Round 11 (Lamps) by Ján Farkaš
- WPC 2015/Round 2 by Andrey Bogdanov
- WPC 2015/Round 14 (Coded)
- WPC 2012/Round 3 (Missing Arrow)
- WPC 2012/Round 7 (Double Arrows)
- WPC 2011/Part 5
- WPC 2011/Part 15
- WPC 2010/Part 9 (Double Arrows)
- WPC 2010/Part 13 (Missing Arrow)