Daily logic puzzle
Numberlink online, a new marsh every midnight.
Numberlink asks you to join each pair of matching endpoints with a path through the grid: paths never cross, never run beside themselves, and when the grid is finished every cell has been used. Ours is called Herons, it is free, and a new one appears at midnight.
- a new marsh at midnight, easy on Monday and eight by eight on Sunday
- exactly one solution, reachable by reasoning, checked by program
- hints that explain the technique, a two step Check, no red ink while you play
Today's marsh. Every pair of nests belongs to one pair of herons.
The rules
Three rules, and that is the whole game.
Numberlink is also published as Arukone, Nanbarinku and, in a looser form, as Flow. The rules below are the strict ones.
- Every pair of nests belongs to one pair of herons. Draw a flight path between the two nests of every pair. A path steps from one cell to the next, up and down or left and right, never diagonally, and it never runs beside itself.
- Paths never cross. Once a cell belongs to one path it is closed to every other.
- Every cell of the marsh is used: no cell is left over when the marsh is finished.
Our name for it
We call it Herons.
The puzzle is known as Numberlink. We call ours Herons because the pairs are nests and the paths are the birds flying between them, and because the rule that every cell must be used reads better as a marsh with nothing wasted than as a covering constraint.
The rules are untouched, and they are the strict ones. Many phone versions of this puzzle let a path double back beside itself and leave cells empty; ours does not, which is what keeps the solution unique.
Where to start
Three ways in.
The archive of past marshes is free as well and goes back a year: Herons archive.
- Play today's marsh
The daily puzzle, easy on Monday and eight by eight on Sunday, new at midnight.
- How to play Numberlink
The rules with a worked example, the controls and the corner arguments worth knowing.
- Practice sets
Sets by difficulty when one marsh a day is not enough.
One solution
A program says so, not a person.
Every puzzle we publish has exactly one solution, and it is a program that decides. The generator throws a candidate away unless the solver returns exactly one solution and unless a second solver, restricted to human style reasoning, finishes it without guessing.
You can see the check yourself: the file tests.mjs in the game folder runs it over thirty days in every size. Numberlink is the kind of puzzle where sloppy construction leaves dozens of valid fillings, so this is the difference between a logic puzzle and a doodle.
While you play, nothing goes red. A mistake is shown only by Check, in two steps: first how many cells are wrong and roughly where, then which ones. Hint works the same way, first the technique and the corner, then the step.
Questions
Questions about Numberlink.
What is Numberlink?
A path puzzle. Pairs of matching endpoints sit in a grid and you join each pair with a path that steps between neighbouring cells. Paths must not cross, must not touch themselves along their own length, and in the strict version every cell of the grid must be covered. It is also known as Arukone and Nanbarinku.
Is it free here?
Yes. The daily puzzle, the practice sets, the archive going back a year, the hints and the Check are all free, with no account and no advertising. We sell printable puzzle books on the same site, and that is the whole business model.
Does every cell have to be used?
Yes, in our version. That is the strict rule and it is what makes the answer unique. Versions that allow empty cells usually have many valid solutions, which is fine as a pastime but is not the puzzle we generate.
Can a path run next to itself?
No. A path may not touch its own length in a neighbouring cell, only step forward. It is the rule that rules out the lazy zigzag filling and the one worth checking when a nearly finished grid refuses to close.
Do I ever have to guess?
No, and that is checked rather than promised. Every published puzzle was solved by a program restricted to reasoning before it was allowed out. If you are stuck, Hint names the technique and the area before it draws a step.
Where can I get more of these on paper?
In the Herons book: one hundred Numberlink puzzles as a printable PDF in A4 and US Letter, with the solutions at the back. There is a free five puzzle sample to look at first. See the <a href="/puzzle-books/numberlink-puzzle-book/">Numberlink puzzle book</a>.
Related
More of the same.
One hundred of these on paper, with the solutions at the back: Numberlink puzzle book (PDF, free sample).
All ten daily games are on one page: daily logic games.
Auf Deutsch: Numberlink online spielen.