Sudoku and Slitherlink are both grid-based logic puzzles you solve by pure deduction, so solvers naturally wonder how alike they really are. The short answer: Slitherlink is distant to Sudoku. Below we lay out what the two share, where they part ways, and whether the skills you have built on Sudoku will carry over.
- Grid: Dots-and-edges grid
- Closeness to Sudoku: Distant
- Also called: Loop the Loop, Fences
What is Slitherlink?
Draw a single continuous loop along the grid lines so that each numbered cell has exactly that many of its four edges used. Here are the rules in full:
- Connect dots with horizontal and vertical segments to form one closed loop.
- A number in a cell says how many of its four edges the loop uses.
- The loop never crosses itself or branches.
What a Slitherlink looks like
A Slitherlink is a grid of numbered cells, and you draw a single closed loop on the grid lines so each number has that many of its four edges used. Here is a small solved one - the purple loop runs around all four "2" cells, giving each exactly two edges.
A solved Slitherlink: the loop gives each "2" cell exactly two of its edges.
Both are pure-logic, single-solution puzzles, and both reward marking impossibilities - here edges that cannot be part of the loop. But you draw a loop on the edges, not digits in the cells, and there is no row, column or region rule. The most distant relative.
What Slitherlink shares with Sudoku
- Both are pure-logic puzzles with a single solution reached without guessing.
- Both reward marking impossibilities - here, edges that cannot be part of the loop.
How Slitherlink differs from Sudoku
- You draw a loop on the edges, not digits in the cells.
- The numbers are edge counts, and there is no row, column or region rule.
Do Sudoku skills transfer?
Nothing places digits here, so no Sudoku technique applies directly - but the discipline of proving each mark before committing is the very habit Sudoku trains.
The verdict
Slitherlink shares Sudoku's logical purity but almost none of its machinery - it's a loop-drawing puzzle, not a filling one.
Where to play it
If it was Sudoku you came for, the level is the choice that matters more than the variant - Slitherlink and Sudoku part ways on the rules, but a Sudoku grid can be a two-minute warm-up or an hour of work depending on nothing but how much of it you are given.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Easy Sudoku leaves 36 of the 81 cells filled, so there is always an obvious next move somewhere; Evil Sudoku leaves 23, with no easy moves at all. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.