How to Play Slitherlink
Slitherlink is widely considered one of the finest Nikoli logic puzzles ever created. The playing field consists of a grid of dots with numerical clues inside some squares. You must draw line segments between horizontally or vertically adjacent dots to form one unbroken loop.
🔢 Clue Values (0-3)
The number inside a cell specifies exactly how many of its 4 boundary segments are part of the loop.
➰ Single Closed Loop
The finished loop must be a single unbroken cycle with no loose ends, branches, or self-intersections.
✖️ Elimination Marks
Marking edges with an 'X' keeps track of impossible paths and guides subsequent deductions.
Fundamental Slitherlink Solving Theorems
- Zero Adjacent Edges: A
0immediately gives you 4 'X' marks around it. Any line reaching a corner of a 0 must turn 90 degrees away from it. - Adjacent Threes (3-3): Two horizontally or vertically adjacent
3s force parallel lines on the outer edges and a segment between them. - Diagonal Threes: When two
3s touch diagonally, the outer corner edges of both cells must be drawn. - Corner Threes: A
3in a corner cell always has its two outer border edges filled in.