Play Numberlink Online
Connect each pair of matching numbers with a continuous path. Paths cannot cross or overlap, and every cell must be filled. A classic flow puzzle — pure logic, no guessing.
Drag from a number to connect pairs — fill every cell
What Is Numberlink?
Numberlink (also known as Arukone, Flow Free, or Nanbarinku) is a logic puzzle played on a rectangular grid. The grid contains pairs of identical numbers (1–1, 2–2, 3–3, etc.). Your goal is to draw a continuous path connecting each matching pair so that:
- No two paths cross or overlap. Each cell belongs to exactly one path.
- Every cell is filled. The paths must cover the entire grid with no empty cells remaining.
- Paths travel horizontally and vertically — no diagonal connections.
Numberlink was first published by Nikoli in Japan, where it appeared in Puzzle Communication Nikoli under the name Nanbarinku. The puzzle has since become wildly popular worldwide, especially in its mobile incarnation as “Flow Free.” The core mechanic — connecting matching endpoints with non-crossing paths — is deceptively simple but yields surprisingly deep logical challenges.
How to Play Numberlink
- Choose a grid size and difficulty. Start with 5×5 Easy to learn the mechanics. Larger grids with fewer clues are harder.
- Drag from any number to begin drawing a path. The path extends through adjacent cells horizontally or vertically.
- Connect to the matching number. Each number appears exactly twice — link each pair with a single continuous path.
- Fill every cell. A valid solution uses every cell in the grid. No empty spaces allowed.
- Paths cannot cross or share cells. If a path would overlap another, rethink your route.
- Check your solution with the Check button, or the puzzle auto-solves when all cells are correctly filled.
Numberlink Strategy Tips
1. Start With Adjacent Pairs
When two matching numbers are next to each other, their path is often just one segment. But be careful — sometimes a direct connection would block other paths. Consider whether you need the path to detour and cover nearby empty cells.
2. Work From Edges and Corners
Numbers in corners and along edges have fewer possible directions. This reduces their path options and makes them easier to solve first. Corner endpoints especially often have only one or two viable routes.
3. Watch for Bottlenecks
A bottleneck is a narrow passage where only one path can physically fit. If two endpoints are on opposite sides of a bottleneck, their path must go through it. Identifying bottlenecks early dramatically narrows the possibilities.
4. Avoid Isolating Empty Cells
Since every cell must be filled, watch out for empty areas that no path can reach. If your current paths would leave an isolated pocket, something is wrong — backtrack and reroute.
5. Think About Parity
Count the empty cells in a region. If there’s an odd number, an odd number of paths must pass through. This parity reasoning is a powerful advanced technique that can reveal which paths must go where.
6. Use the “One Free Cell” Rule
If a cell has only one empty neighbour left (all others are already filled or blocked), the path using that cell must continue through that neighbour. This forced-move logic chains beautifully and can solve large sections of the grid at once.
Numberlink vs Other Puzzles
- Numberlink vs Sudoku: Both are grid-based logic puzzles, but Sudoku fills numbers while Numberlink draws paths. Numberlink has a stronger spatial and geometric component.
- Numberlink vs Masyu: Masyu draws a single loop; Numberlink draws multiple separate paths. Both require careful path planning.
- Numberlink vs Slitherlink: Slitherlink creates one closed loop using edge clues; Numberlink connects specific pairs through cells.
- Numberlink vs Hashi: Hashi connects islands with bridges; Numberlink connects number pairs with paths. Both involve connecting endpoints in a non-crossing way.
- Numberlink vs Flow Free: Flow Free is essentially the same puzzle, popularised as a mobile app. The rules are identical — connect pairs, fill the grid, no crossing.
History of Numberlink
Numberlink traces its origins to Nikoli, the legendary Japanese puzzle publisher based in Tokyo. It appeared in Puzzle Communication Nikoli as Nanbarinku (ナンバーリンク), alongside other now-famous puzzles like Sudoku, Kakuro, and Masyu.
The concept — connecting labelled endpoints with non-crossing paths on a grid — is closely related to problems in graph theory and VLSI circuit routing. Mathematically, it’s a variant of the edge-disjoint paths problem, which is NP-complete in general but highly tractable on small grids with good puzzle design.
The puzzle reached a global audience through the mobile app Flow Free, released in 2012, which brought the concept to millions of casual gamers. The game mechanic has also appeared under names like Arukone and Number Connection in various puzzle magazines and competitions.
Today, Numberlink is a staple of puzzle competitions including the World Puzzle Championship, where solvers face large grids under time pressure. Its elegant rules and deep logic make it a favourite among both casual and competitive puzzle enthusiasts.
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