Slitherlink (also Fences) is a loop puzzle on a dot grid. Numbers in cells tell you how many of that cell's four edges belong to the loop. Draw a single closed loop that satisfies every clue—deductive and visual.
Rules
Draw a single closed loop by connecting adjacent dots. The loop does not cross or branch. Each cell number 0–4 means exactly that many of its four edges are part of the loop. Empty cells have no constraint. Every dot has 0 or 2 segments. Key patterns: a 3 in a corner forces two specific segments; adjacent 3s share a segment; 0 next to 3 forces the loop away from the 0; a chain of 3s forces a straight line. Solve by logic; unique solution.
History
Nikoli published Slitherlink in 1989; "Fences" is the marketing name in Western puzzle books. Culture-independent design enabled global spread. Simon Tatham and Conceptis offer digital implementations. One of Nikoli's most successful exports.
Strategy tips
Master corner patterns first: a 3 in a corner forces two segments. Use dot connectivity—every dot has 0 or 2 segments, so if a dot already has 2, it's closed. Trace the loop mentally and check for illegal branches. Adjacent 3s constrain each other; 0s eliminate edges.
Cultural context
One of Nikoli's most globally successful puzzles; "Fences" in Western puzzle books. Dedicated Slitherlink apps; crossover with competitive puzzle solving. Slitherlink is a loop puzzle on a dot grid; numbers tell you how many edges of each cell belong to the loop. Culture-independent design enabled global spread. Available on Nikoli.com, Conceptis Puzzles (Fences), and Simon Tatham's Portable Puzzle Collection.
Where to buy / play
- Slitherlink / Fences Puzzle Book (Nikoli) Official Nikoli slitherlink collection
- Play Slitherlink free in browser (Simon Tatham — Loopy) Free, open-source browser implementation — choose 'Slither' grid type