Hashi

Rules

Draw some horizontal and vertical lines so that all the circles are connected (directly or through connections through other circles). No two circles may be directly connected by more than two lines. Lines may not cross other lines. If a circle is numbered, then that number represents the number of lines that are connected to that circle.

(Rules from PGP IB and example from WPC 2018 IB)

History of the puzzle

First appeared on Nikoli volume 31 (1990). Invented by れーにん ("Renin"). Originally named 橋をかけろ ("Lay bridges").

Appearances in the past WPCs

• WPC 2019/Team Playoffs (Knapp Daneben) by Erhard Notz
• WPC 2019/World Cup Playoffs by Erhard Notz
• WPC 2018/Round 2 by Jiří Hrdina
• WPC 2016/Round 12 by Matúš Demiger
• WPC 2014/Round 3
• WPC 2014/Round 6
• WPC 2013/Part 9
• WPC 2010/Part 2
• WPC 2010/Part 13 (Desert Islands)