Slitherlink was invented by Nikoli and first appeared in 1989.
Puzzle and Goal
A standard unsolved puzzle consists of a rectangular grid containing some numbers ranging from 0 to 3.
The goal is to draw a loop along the edges of the grid.
The solved grid must satisfy the following conditions:
Each number clue indicates the number of sides of the containing cell that contain a segment.
There is no restriction on the number of sides for cells that do not contain clues.
The resulting loop is a Jordan curve (that is, it is a single non-intersecting closed loop).
Slitherlink grids can also have other geometric patterns, in which case the maximum number is one less than the number of sides of the largest polygon in the grid.
Dotty Dilemma; Fences; Gartenzaun; Great Wall of China; Heiliger Pfad; Loop the Loop; Loopy; Number Line; Ouroboros; Rundweg; Schlangenlinie; Sli-Lin; Suriza; Surizaarinku; Takegaki