# Four Winds

## Rules[edit]

Draw horizontal and vertical lines, starting in the numbered cells, so that each empty cell is used by exactly one line. Each number indicates how many cells are covered by lines starting in this cell, not counting the numbered cell itself. Aside from their starting cells, lines cannot enter cells with numbers.

(Rules from WPC 2019 IB, example from PGP IB)

### Rule variations[edit]

- Sometimes, there is no rule that specifies all cells to be visited.
- On Hexagonal grids this puzzle is called
**Six Winds**for an obvious reason.

## History of the puzzle[edit]

First appeared on *Puzzler* magazine in 1990. Invented by Norihiko Fujimaki (Japan). Originally named ウォールロジック ("Wall Logic").

## Variants[edit]

### Six Winds with Hooks[edit]

First appeared on WPC 2018/Round 4. Written by František Luskač (Czech Rep.)

Draw hooked lines, starting in the numbered cells, so that each empty cell is used by exactly one line. Each line is hooked at the end: It means that it turns one cell back at the angle of 60 degrees. The minimum length of each hooked line is 3. Each number indicates how many cells are covered by lines starting in this cell, not counting the numbered cell itself. Aside from their starting cells, lines cannot enter cells with numbers.

(Example from WPC 2018 IB)

## Appearances in the past WPCs[edit]

- WPC 2019/World Cup Round 1 by Roland Voigt
- WPC 2018/Round 2 by Jiří Hrdina
- WPC 2018/Round 4 (Hexagonal) by Jan Novotný
- WPC 2018/Round 4 (Six Winds with Hooks) by František Luskač
- WPC 2017/Round 3 by Rohan Rao
- WPC 2017/Round 10 ("Optimizer") by Rohan Rao
- WPC 2016/Round 14 (part of a Permaculture hybrid) by Matúš Demiger
- WPC 2014/Round 14
- WPC 2012/Part 3 (High Wind)
- WPC 2012/Part 7
- WPC 2011/Part 5
- WPC 2010/Part 2