Slitherlink
JAPANESE LOGIC PUZZLE by NIKOLI (1989) — solver draws a SINGLE CLOSED LOOP along a grid of dots, satisfying constraints given by NUMBERS INSIDE CELLS. Number indicates how many of the cell's 4 SIDES are part of the loop (0-3). Signature: LOOP MUST BE SINGLE + NON-SELF-CROSSING. Elegant, pure logic — no arithmetic, no words. Enormously popular in Japan + Nikoli's international puzzle magazines. Considered one of Nikoli's finest logic puzzle inventions alongside Sudoku + Kakuro.
Quick facts
Category
Puzzle Games
Type
Individual
Players
1–1
Duration
~20 min
Where played
indoor
Country of origin
🇯🇵 Japan
Estimated origin
1989 Nikoli publication; global spread via puzzle magazines + apps 2000s+
Olympic
No
Popularity
regional
How it works
Objective
Draw a single closed non-self-crossing loop along the grid that satisfies all numeric clues.
Rules
Basic rules
Grid of DOTS with cells; some cells contain numbers 0, 1, 2, or 3
Signature grid + clues.
Draw HORIZONTAL or VERTICAL line segments between adjacent dots
Signature edges.
NUMBER indicates how many of that cell's 4 SIDES have a line
Signature edge count clue.
SINGLE CLOSED LOOP — no branches, no crossings, no separate loops
Signature loop constraint.
Cells WITHOUT numbers have no constraint (may have 0-4 sides on loop)
Standard blank cells.
UNIQUE SOLUTION for well-designed puzzles
Puzzle quality.
Scoring
Complete valid single-loop = puzzle solved.
| Action | Points |
|---|---|
| Valid single closed loop satisfying all clues | Puzzle solved |
| Multiple loops, self-crossing, or violated clue | Invalid |
Win condition · Complete valid loop.
Equipment
Slitherlink grid + pen/pencil
Paper puzzle; app + online versions common
Terminology
- Slitherlink
- Nikoli's Japanese name; also known as Fences, Loop the Loop.
- 0 cell
- No sides on loop → all 4 sides must be BLANK.
- 3 cell
- 3 sides on loop → often quickly deducible.
- Nikoli
- Japanese puzzle publisher; popularized Sudoku, Kakuro, Slitherlink globally.
Where it is played
Famous names & records
Famous athletes
- Various Nikoli-published Slitherlink constructors
- Puzzle Championship regulars (World Puzzle Federation events)
Sources & provenance
- Wikipedia — Slitherlink— Wikipedia
- Nikoli — Slitherlink— Nikoli