Slitherlink
Connect adjacent grid dots with orthogonal lines to construct a single, continuous, non-intersecting loop that satisfies surrounding numerical clues.
HISTORICAL ORIGIN LORE
The Lineage of Slitherlink
Invented by Japanese publisher Nikoli and first published in Puzzle Communication Nikoli No. 26 in 1989. Known variously as Takegaki (bamboo fence), Fences, or Loop the Loop, it has been widely studied in computational complexity as an NP-complete problem exhibiting topological purity.
SYSTEM MECHANICS & RULES
Rules & Cognitive Architecture
A rectangular lattice of dots containing numbers 0, 1, 2, or 3 inside selected cells.
Draw horizontal and vertical line segments between adjacent dots.
A number in a cell specifies exactly how many of its four bounding edges are part of the loop.
Cells without numbers may have any number of edges.
Lines must form exactly one single closed loop with no branches, crossings, or loose dead ends.
Trained Mental Models
- ▸Topological loop closure intuition and Jordan Curve inside/outside logic
- ▸Corner vertex parity and degree-2 constraint enforcement
- ▸Local pattern recognition (diagonal 3s, adjacent 3-0 corners)
INCLUDED FREE FOREVER
The Three Base Tiers
Gentle
5×5 and 6×6 lattices with standard corner patterns providing immediate, satisfying progress.
Standard
7×7 grids requiring line-avoidance logic around 0s and parallel run deductions.
Deep
8×8 grids with sparse clues requiring Jordan Curve theorem inside/outside loop parity.
BEYOND+ MASTER EDITIONS
The Master Variants for Slitherlink
8×8–12×12 Master Grids
Expansive square lattices with deep non-local topology deductions
Large-scale square lattices with minimal clue density, demanding long-range loop planning and global loop parity tracking to avoid premature sub-loops.
- ·Sub-loop prevention algorithms
- ·Minimal clue density optimization
- ·Jordan Curve parity validation engine
Honeycomb 37/61/Snowflake
Non-Euclidean hexagonal planar tessellations with 6-way loop geometries
Abandons square geometry in favor of hexagonal planar honeycombs (37 and 61 hex cells) and symmetric snowflake lattices. Each hex cell features up to 6 bounding edges, unlocking entirely new loop theorems.
- ·Hexagonal planar graph embedding
- ·6-degree vertex routing rules
- ·Radially symmetric snowflake clue generators
FREQUENTLY ASKED QUESTIONS
Questions on Slitherlink Architecture
Can the loop branch or intersect in Slitherlink?
No. Every vertex in the loop must connect exactly two edges—no dead ends, no three-way junctions, and no self-intersections.
What is the Honeycomb variant in Beyond+?
Honeycomb Slitherlink maps the puzzle onto hexagonal grids where numbers range from 0 to 5, generating organic, curved loop paths.
How do you prevent smaller loops from closing prematurely?
You must always ensure that any line segment can continue to connect to all other active segments, maintaining a single unified loop component.
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Play Slitherlink on Android
Available directly on Google Play with Gentle, Standard, and Deep tiers included free forever.