Slitherlink
How to solve Slitherlink: one loop, step by step
Updated Tuesday, October 27
To solve a Slitherlink, cross out every side of the 0s, then follow one rule at every dot: the loop arrives and leaves, so a dot has 0 or 2 lines. Pairs of 3s and the corners of the grid give the first lines. Every Gridarium slitherlink can be finished this way, without guessing.
The rules
Join neighbouring dots with lines to make one single closed loop. It never crosses itself and never branches. A number in a square says how many of its four sides the loop uses; a square without a number can use any.
Step 1: the 0s
A 0 uses none of its sides: put a cross on all four. Those crosses are the start of everything else.
Step 2: every dot has 0 or 2 lines
The loop passes through a dot or stays away from it. A dot with two lines has crosses on its other sides; a dot with one line and only one way out continues that way; a dot with no way out but one has no line at all.
Step 3: pairs of 3s and corners
Two 3s side by side always use the line between them and the two lines beyond them. A 3 in a corner of the grid uses both outer sides of that corner. A 1 in a corner uses neither outer side.
Step 4: no small loops
The loop is one piece. A line that would close a small loop while other lines are still apart cannot be drawn: cross it.
Step 5: what if
On the biggest grids, look at one side and ask what would follow if the line went there. If it leads at once to a dot with three lines, or a number with too many sides, it is a cross.
The three levels
- Easy: 5 by 5 squares.
- Medium: 7 by 7 squares.
- Hard: 10 by 10 squares.