How Do You Play Slitherlink? Rules and Basic Solving Steps

Slitherlink (also called Fences or Loop the Loop) is a logic puzzle where you draw a single closed loop along the grid lines between dots. Each number in a cell tells you how many of its four surrounding edges belong to the loop. You can play it online at puzzle-loop.com, where the page describes the rules as "simple rules and challenging solutions" and offers board sizes from 5x5 up to 25x30, plus daily, weekly, and monthly specials.

The rules in plain terms

• Draw one loop. Connect dots with lines so the result is a single continuous cycle.
• No crossings, no branches. A dot can be part of the loop with exactly two connected edges — never one (a dead end) or three or more (a branch).
• Numbers count surrounding edges. A cell marked 2 must have exactly two of its four sides drawn; a 0 has none; a 3 has three.
• Unnumbered cells are unconstrained by a count, but still obey the single-loop rule.

Controls on puzzle-loop.com

The site's own instructions are short: left click between the dots to connect them, and right click to mark an edge with X to show it is excluded. The page also lists optional aids such as auto-crossing the sides of completed numbers, highlighting wrong moves, and a ghost-lines mode. If the game does not load, the page notes that JavaScript must be switched on; a printable copy is available as an alternative.

A practical solving order

Start with the clues that force the most, then work toward the ambiguous middle.

1. Handle 0s first. Every edge around a 0 is excluded — mark them all with X. This often forces neighboring 3s.
2. Fill in 3s. A 3 means only one of its four edges is empty, so the other three are loop. Around a 3 next to a 0, the shared edge is already excluded, which can pin down the rest.
3. Use 1s and 2s to eliminate or force. A 1 next to a 3, for example, shares edges that cannot both be used, so you can often cross out candidates.
4. Watch the corners and borders. Cells on the edge of the grid have fewer neighbors, so their numbers constrain more tightly.
5. Avoid dead ends and second loops. Every time you add a line, check that no dot ends up with only one connection and that you are not closing a small separate cycle. The final loop must be one continuous cycle.
6. Verify at the end. Walk the loop and confirm each number matches the count of drawn edges around it, and that no dot has a branch.

What to expect as you go

The page offers 5x5 and 7x7 boards in Normal and Hard, up through 25x30, so you can start small and scale up. Larger boards mainly add more deduction steps rather than new rules. If you get stuck, the site's toolbar includes options like highlighting wrong numbers and showing checkpoints, which can help you spot a contradiction without revealing the whole solution.

Once your loop is closed and every number checks out, the puzzle is solved.