KNS Puzzles offers the Slitherlink puzzles in the following formats:
5 x 5 - Level 1 - Level 2 - Level 3
7 x 7 - Level 1 - Level 2 - Level 3
10 x 10 - Level 1 - Level 2 - Level 3
15 x 15 - Level 1 - Level 2 - Level 3
20 x 20 - Level 1
Join the dots to create a single continuous loop. The numbers indicate how many of the four surrounding sections contain a line. The loop never crosses itself and any given dot can only have a maximum of two lines passing through it. What are the numbers for? These tell you how many lines surround that square.
A 0 clue means that there is no loop around this square, and we can mark all of the edges with crosses. A 3 and a 0 together. As we have a zero, this cannot be a line, and the other three must be, and the loop carries on both sides.
Two 3's together. No matter where loop goes, these will always be lines. Two 3's diagonally. No matter where loop goes, these will always be lines.
A 3 and a 0 diagonally. No matter where loop goes, these will always be lines. 3 in a corner. No matter where loop goes, these two will always be lines.
2 in a corner. No matter where loop goes, these two will always be lines. 1 in a corner. No matter where loop goes, these cannot be lines.
This is the start of the puzzle.
These 0 clues mean that there are no lines surrounding these squares, so we can mark them with crosses.
There is only one way of having 3 lines around this square, as we already have a cross along the bottom.
There are now only remaining 2 places for the loop to go for this 2 clue.
This is the only route allowed for the loop, to avoid the crosses we have.
There are now some crosses we can add, either because we've satisfied a clue, or a line would create a loop that's not allowed.
We have to satisfy the 2 clue, and this creates some crosses and the loop must go this way.
The loop must go this way to satisfy the 2 clue, which completes the 1 clue as it passes.
The loop must go this way to satisfy the 2 clue, which adds crosses and the loop continues around the bottom.
This is the only route for the loop, remembering to add crosses as we go, and the puzzle completes.
The completed puzzle.