Draw a single, non-intersecting loop that only consists of horizontal and vertical segments between the dots. A number inside a cell indicates how many of the edges of that cell are part of the loop.
(Rules and example from PGP IB)
History of the puzzle
First appeared on Nikoli volume 26 (1989). The rule was suggested by 矢田レーニン ("Yada Renin"). Originally named スリザーリンク.
Originally the puzzle was presented like Bosnian Road. It took the current form when Nikoli merged the elements of a different puzzle called ナンピツ ("Nanpitsu," suggested by 轟由紀 ("Todoroki Yuki"), first appeared also in 1989).
See list of Slitherlink variants.
Appearances in the past WPCs
Listed here are appearances of classic to almost-classic Slitherlink. For variants, see list of Slitherlink variants#Appearances in the past WPCs.
- WPC 2019/Round 3 (Permaculture hybrid with Domino Hunt) by Silke Berendes
- WPC 2019/World Cup Round 1 (Hexagonal) by Roland Voigt
- WPC 2019/Round 4 by Roland Voigt
- WPC 2019/Round 8 by Gabi Penn-Karras
- WPC 2019/Round 9 by Ulrich Voigt
- WPC 2019/World Cup Playoffs by Gabi Penn-Karras
- WPC 2018/Round 4 (Hexagonal) by Jan Novotný
- WPC 2018/Round 4 (Cairo Pentagonal) by František Luskač
- WPC 2018/Round 7 by Jiří Hrdina
- WPC 2018/Round 13 (Knapp Daneben) by Jiří Hrdina
- WPC 2018/Individual Playoffs (Hexagonal, unused) by Jan Novotný
- WPC 2017/Round 1 (Coded) by Ashish Kumar
- WPC 2017/Round 5 (Irregular Grid) by Prasanna Seshadri
- WPC 2017/Round 9 by Ashish Kumar
- WPC 2016/Round 2 by Matej Uher
- WPC 2016/Round 9 by Matúš Demiger
- WPC 2016/Round 15 (part of a Matchmaker puzzle) by Matej Uher
- WPC 2015/Round 2 by Anton Titov