Divide the grid along the given lines into some squares and rectangles. A number between two regions must be equal to the sum of the areas of these regions. Numbers always lie at borders, not inside the regions. There can be rectangles that do not touch any of the given clues.
(Rules and example from WPC 2016 IB)
- In the original by Naoki, all rectangles were required to share an edge with at least one number. However, this rule was dropped in a puzzle from WPC 2016/Round 8.
History of the puzzle
Invented by Naoki Inaba (Japan) in 2003. First appeared on his website.
Appearances in the past WPCs
- WPC 2016/Round 8 by Matej Uher