Play Number loop puzzle (Loopy) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
In this loop puzzle you join dots into one closed loop, guided by numbers that tell you how many of the surrounding edges belong to it. It is best known from the Japanese publisher Nikoli under the name Slitherlink. This version plays on square grids and on many other tilings. The puzzle is ready below; click an edge to draw part of the loop.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Mark an edge as part of the loop | — | Left-click the edge (again to undo) |
| Mark an edge as not part of the loop | — | Right-click the edge (again to undo) |
| Undo / redo | U / R (or Ctrl+Z / Ctrl+R) | Game menu buttons |
| Show the solution | — | Game menu → Solve |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Loopy is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
- Draw a single continuous loop along the grid's edges, with no branches and no crossings.
- A number inside a cell says exactly how many of that cell's edges are part of the loop.
- Cells without numbers can have any number of loop edges.
Sizes and difficulty
The square-grid presets come at 7×7 and 10×10 in Easy, Normal and Hard. The Type menu also has triangular, snub-square, Cairo, kites and two Penrose tilings, and a "More..." submenu with honeycomb, octagonal, dodecagonal, hat and spectre grids among others. The square, triangle and honeycomb grids are the easiest to read.
Solving tips
Begin with 0s: cross out all their edges. On a square grid a 3 next to a 0 fixes three edges at once, and two adjacent 3s always share their middle edge plus the two parallel outer edges. Every dot has either zero or two loop edges, so a dot with one drawn edge and only one free option must continue that way, and a dot with two crossed-out edges of three is forced. Right-clicking known non-edges keeps the picture readable.
Where this puzzle comes from
Loopy is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
Can the loop touch itself or branch?
No. It must be one closed path that visits each dot at most once, so every dot has either zero or two loop edges.
What do the different grid types change?
Only the shape of the cells. The rule is the same; on grids with more sides per cell the numbers can be higher and the deductions look different.
Is Loopy free to play here?
Yes, with no limit on the number of puzzles. Loopy is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
More you can play in your browser
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Want a game like this on your own site?
Number loop puzzle (Loopy) isn't ours to give away — we host it, we didn't write it. But eleven of the games here we did write from scratch, and those are free for anyone to put on their own page: one line of HTML, no account, no permission, no attribution beyond a credit line.