Shade some cells to create diagonal chains. Shaded cells cannot be horizontally or vertically adjacent, and no shaded cell can touch more than two other shaded cells diagonally. Furthermore, there can be no “rings” – each group of diagonally connected cells must have at least one shaded cell with less than two diagonally touching shaded neighbours. Cells with numbers cannot be shaded.
The numbers indicate the sum of the lengths of all such chains where at least one shaded cell is horizontally, vertically or diagonally neighbouring to the numbered cell.
(Rules and example from WPC 2019 IB)
History of the puzzle
Appeared on WPC 2019/Round 12, an "innovations" round. The puzzles were written by Ulrich Voigt.
Appearances in the past WPCs
- WPC 2019/Round 12 by Ulrich Voigt