Daily logic puzzle
Nurikabe online, a new meadow every midnight.
Nurikabe is a shading puzzle: every number marks an island of exactly that many cells, islands never touch side by side, and everything else is one connected sea that never fills a two by two block. Ours is called Voles, it is free, and a new one appears at midnight.
- a new meadow at midnight, easy on Monday and twelve by twelve 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 meadow. Each number is a vole family and says how big their island is.
The rules
Three rules, and that is the whole game.
Nurikabe is also published as Islands in the Stream and Cell Structure. The rules are the same under every name.
- Every number is a vole family, and it says how big their island is, the number's own cell included. Shade the rest of the meadow as water so that every island holds exactly one number and exactly that many cells.
- Islands never touch by a side. Two islands may sit corner to corner, never side by side, or they would be one island with two numbers.
- The water always hangs together as a single sheet, and no two by two block is ever all water.
Our name for it
We call it Voles.
The puzzle is known as Nurikabe, after a Japanese wall spirit that blocks a traveller's path. We call ours Voles because the meadow floods and each number is a family on an island of its own size, and because the two rules that beginners forget, that the water must stay connected and must never form a two by two pool, make plain sense once the shading is water.
The rules are untouched. The standard techniques all apply: cells between two numbers are water, a cell that would strand water is an island, and an island that is full gets a ring of water around it.
Where to start
Three ways in.
The archive of past meadows is free as well and goes back a year: Voles archive.
- Play today's meadow
The daily puzzle, easy on Monday and twelve by twelve on Sunday, new at midnight.
- How to play Nurikabe
The rules with a worked example, the controls and the openings worth learning.
- Practice sets
Sets by difficulty when one meadow 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. The connectedness of the water and the two by two rule are part of that check, not an afterthought.
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 region, then the cell.
Questions
Questions about Nurikabe.
What is Nurikabe?
A shading puzzle on a grid. Some cells carry numbers. Each number belongs to an island of unshaded cells of exactly that size, counting the numbered cell itself, and every island holds exactly one number. Everything else is shaded as one connected sea that never contains a two by two shaded block. It is also published as Islands in the Stream.
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.
Can two islands touch?
Only at a corner. If two islands shared a side they would be a single island with two numbers, which the rules forbid. That is why the cell between two numbers is always water, and it is usually the first thing to fill in.
Why can the sea not have a two by two block?
Because the rule is what makes the puzzle solvable by reasoning. Without it a huge number of shadings would fit the numbers. In practice the rule works for you: any cell that would complete a two by two pool must belong to an island.
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 shades anything.
Where can I get more of these on paper?
In the Voles book: one hundred Nurikabe 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/nurikabe-puzzle-book/">Nurikabe puzzle book</a>.
Related
More of the same.
One hundred of these on paper, with the solutions at the back: Nurikabe puzzle book (PDF, free sample).
All ten daily games are on one page: daily logic games.
Auf Deutsch: Nurikabe online spielen.