Loopy

Loopy (also known as Slitherlink) challenges you to draw a single closed loop around a grid so that each numbered cell has exactly that many of its edges in the loop—pure logic, no guessing required.

Played on a rectangular grid of dots, the goal is to draw a single, continuous, non-intersecting loop along the grid lines—never branching or crossing itself—based solely on numerical clues.

Each cell in the grid may contain a number (0 to 3), indicating exactly how many of its four edges are part of the loop. Cells with no number impose no constraint. Using deduction, players gradually determine which edges must be part of the loop and which must be excluded, until the full closed loop emerges.

Despite its minimalist rules, Loopy offers deep logical challenges. Solving requires careful reasoning about connectivity, parity, and local constraints—often revealing elegant patterns and satisfying “chain-reaction” deductions. Every puzzle is guaranteed to have a unique solution reachable through logic alone, with no guessing needed.

Form a single closed loop along the grid edges such that every numbered square has exactly that many of its edges included in the loop.

Click on a grid edge to mark it as part of the loop (black); click again to revert it to undecided (yellow). Right-click on a grid edge to mark it as definitely not part of the loop (faint grey); right-click again to return it to undecided.

Once you've mastered the square grid, explore the Type menu for many other tiling styles!