LoopcairnPlay Slitherlink

How to play Slitherlink

Draw horizontal and vertical lines between neighboring dots. Your finished drawing must be one closed loop.

  1. A number tells you exactly how many of that square’s four edges belong to the loop. A 0 has no lines beside it; a 3 has three.
  2. An empty square has no number restriction. It is not a zero.
  3. The loop cannot branch, cross itself or break into separate loops. Every dot used by the loop has exactly two lines.
A two by two example. Each square has a 2. One loop around the outside gives every square two bordering lines.2222
Each 2 touches two of the drawn edges. The inner edges stay empty, and all the lines form one loop.

Start with a zero

Mark crosses on the four edges around a 0. A cross is a note that an edge cannot be part of the loop. You do not need to cross every unused edge to finish.

At a dot, two lines already drawn mean the other edges must stay empty. If a dot has only one line, that line still needs a way to continue.

Draw and correct a mark

Tap an edge to cycle through line, cross and empty. For a larger touch target, use the four arrow buttons to select an edge, then choose Line, Cross or Clear. Undo reverses the last change in this tab. Restart asks before clearing the board.

On the keyboard, arrows move edge selection. Enter or Space cycles a mark; L draws, X crosses, and E or Delete clears. U undoes. Tab moves to the next control outside the board.

Use a hint

Hint checks your current marks. It highlights a line that continues the solution. If a mark blocks the solution, it offers to clear that mark. Applying either kind of hint can be undone.

Practice and Daily

Loopcairn has 24 original puzzles: eight each on 3 × 3, 4 × 4 and 5 × 5 grids. Practice starts with a small board. Daily selects from the same eight-board set for your chosen size at midnight UTC, so boards repeat. Your last selected Daily stays open when you return. Choose Play today’s puzzle to switch dates; an unfinished board asks first.

Progress is saved in this browser. If storage is blocked or a record cannot be read, the game explains the problem and keeps that record unchanged until you choose a recovery action.

Continue in practice returns to your saved practice puzzle at this size. Next puzzle asks before leaving an unfinished practice puzzle with moves. Its saved progress stays in the collection; cycle through the puzzles to return.

Play the first puzzle →