The History of Slitherlink: Nikoli's Loop Puzzle

Slitherlink feels timeless, the kind of clean, elegant logic puzzle that could have been around for a century. In fact it is a modern invention with a clear origin, a meaningful original name, and a journey that took it from a Japanese puzzle magazine to newspapers, books and screens across the world. It comes from the same workshop that gave us Sudoku, and its story is a neat illustration of how a great idea finds a global audience. Here is where Slitherlink came from and how it became a logic classic. When you are done, you can play one yourself.

A puzzle from the house of Nikoli

Slitherlink was created and popularised by Nikoli, the legendary Japanese puzzle publisher. The name should ring a bell: Nikoli is the company that took an obscure American puzzle, refined it, renamed it Sudoku, and set off a worldwide craze. The same workshop is responsible for a whole family of beloved logic puzzles, including Kakuro, Nurikabe and Hashiwokakero, and Slitherlink is one of its finest.

Slitherlink first appeared in Nikoli's flagship magazine, Puzzle Communication Nikoli, in the late 1980s. Like all Nikoli puzzles, it was built on a strict design philosophy: every puzzle is handcrafted rather than churned out by a computer, has exactly one solution, and can be solved by logic alone, with no guessing. That commitment to elegant, fair, hand-made puzzles is a big part of why Nikoli's titles feel so satisfying, and Slitherlink is a perfect showcase for it.

What the original name means

Before it was "Slitherlink," the puzzle had a Japanese name: Takegaki (竹垣), which means "bamboo fence." It is a lovely, fitting image, because the finished loop weaves around the cells of the grid like a fence enclosing a garden. The English name "Slitherlink" came later, an evocative coinage that captures the way the loop slinks and links its way across the board.

The puzzle is also widely known by other names, including Loop the Loop, Loopy and Fences, depending on where you meet it. We cover that naming story in full in our piece on Slitherlink, Loop the Loop and Fences.

Why it stuck around

Plenty of clever puzzles are invented and forgotten. Slitherlink endured because it hits a rare sweet spot:

• The rules are tiny. Draw a single closed loop, and make each numbered cell use exactly that many of its edges. You can learn it in a minute.
• The depth is enormous. Those simple rules generate genuinely deep deductions, especially on large grids where clues are sparse and the single-loop rule does the heavy lifting.
• It is visual and elegant. Watching one clean loop emerge from a scatter of numbers is uniquely pleasing, a different satisfaction from filling in cells.

That blend of a one-sentence rulebook and surprising depth is the hallmark of a great Nikoli puzzle, and it carried Slitherlink out of the magazine and into the wider world.

A puzzle that crosses borders

Slitherlink turned out to travel exceptionally well. Built from numbers and lines rather than words, it needs no translation, and it found enthusiastic audiences far beyond Japan. It became a fixture of newspaper puzzle pages and puzzle books across Europe, the Americas, Asia and Oceania, and a staple of the international puzzle-championship scene, where solvers race through loop grids against the clock.

It also attracted interest from a less expected quarter: mathematicians and computer scientists. The puzzle's single-closed-loop structure connects neatly to ideas in graph theory, and its general form turns out to be surprisingly hard for computers, a story we tell in the graph theory behind Slitherlink. Few puzzles manage to be a relaxing pastime and a serious mathematical object at the same time.

Where it stands today

Slitherlink now sits comfortably in the canon of classic logic puzzles, alongside its Nikoli siblings. It is available in puzzle books, on dedicated puzzle sites, and in apps and collections worldwide, in grid sizes from quick 5×5 starters to sprawling expert challenges. Not bad for a humble loop of lines born in a Tokyo puzzle magazine.

The next chapter of Slitherlink's history is the one you write every time you close a loop. Play Slitherlink now, or learn the rules if you are new to it.

Frequently asked questions

Who invented Slitherlink?

Slitherlink was created and popularised by Nikoli, the Japanese puzzle publisher also responsible for popularising Sudoku and many other logic puzzles. It first appeared in Nikoli's magazine, Puzzle Communication Nikoli, in the late 1980s, built on the company's tradition of handcrafted puzzles with a single logical solution.

What does Takegaki mean?

Takegaki (竹垣) is the original Japanese name for Slitherlink, and it means "bamboo fence." The name pictures the finished loop as a fence woven around the cells of the grid, the same idea behind the English alias "Fences."

Is Slitherlink related to Sudoku?

Slitherlink and Sudoku are different puzzles, but they share a family: both were popularised by the Japanese publisher Nikoli and follow the same philosophy of handcrafted puzzles with a single solution solvable by pure logic. Slitherlink is about drawing a loop, while Sudoku is about placing digits.

How old is the Slitherlink puzzle?

Slitherlink is a modern puzzle that first appeared in Nikoli's magazine in the late 1980s, so it dates from that era rather than from any older tradition. It spread internationally over the following decades to become a widely recognised logic-puzzle classic.