Slitherlink

ONE LOOP

Tap an edge to cycle line → ✕ → clear; drag to continue a line.

ONE LOOP

Slitherlink

A single closed loop always splits the page into an inside and an outside. So every cell is simply in or out, and a loop edge is just where in meets out — Slitherlink is a colouring puzzle wearing a drawing puzzle's clothes.

RULES

  • Each number counts the loop edges around its cell.
  • The loop never crosses or branches — exactly one closed line.

CONTROLS

  • Tap an edge to cycle line → ✕ → clear; drag to continue a line.
  • Arrow keys move the cursor between dots; hold shift and arrow to cycle the edge in that direction.
constructing a layout…

Related: Kirchhoff, another puzzle where one global constraint reduces to a graph computation, and Nurikabe, its connectivity dual — colouring cells in and out instead of drawing a loop between them.