What is Yajilin (Arrow Loops)?

Yajilin is a renowned Nikoli pencil puzzle invented in 1999. Players read arrow clues to position black squares so that no two black squares share an edge, and then draw a single unbroken closed loop passing through every remaining non-clue cell.

Can the loop go through clue squares?

No. Clue squares (squares with arrows and numbers) are barriers. The loop cannot enter or pass through any clue square.

Can two black squares touch?

Black squares cannot touch orthogonally (up, down, left, or right). However, they are permitted to touch diagonally at their corners.

Must every non-black cell be visited by the loop?

Yes. Every single empty cell that is not marked as a black square must be visited by the single continuous closed loop.

Can there be black squares not indicated by arrows?

Yes! Black squares can exist anywhere to allow the loop to visit all remaining cells, as long as they do not violate any arrow clues in their respective rows or columns.

What is Yajilin (Arrow Loops)?

Yajilin is a renowned Nikoli pencil puzzle invented in 1999. Players read arrow clues to position black squares so that no two black squares share an edge, and then draw a single unbroken closed loop passing through every remaining non-clue cell.

Can the loop go through clue squares?

No. Clue squares (squares with arrows and numbers) are barriers. The loop cannot enter or pass through any clue square.

Can two black squares touch?

Black squares cannot touch orthogonally (up, down, left, or right). However, they are permitted to touch diagonally at their corners.

Must every non-black cell be visited by the loop?

Yes. Every single empty cell that is not marked as a black square must be visited by the single continuous closed loop.

Can there be black squares not indicated by arrows?

Yes! Black squares can exist anywhere to allow the loop to visit all remaining cells, as long as they do not violate any arrow clues in their respective rows or columns.

Nikoli Classic • Arrow Loops

Yajilin (Arrow Loops)

Place black blocks along directional arrow rays and weave a single unbroken loop visiting every single remaining square!

Warmup • 5×5

⏱ 0:00

🏹 Arrow Clues:4 / 6

Black Cells:0

Drawing Yajilin arrow rays...

Yajilin Rules & Objective

Invented by Nikoli in 1999, Yajilin (Arrow Ring) balances spatial pathfinding with directional deduction:

1. Arrow CluesAn arrow with a number N indicates exactly N black squares in that ray line of sight. Clues themselves are never black and never visited by the loop.

2. No Orthogonal AdjacencyBlack squares may touch at corners diagonally, but two black squares can NEVER share an edge. Placing a black square instantly protects its 4 orthogonal neighbors.

3. Single Closed LoopThe loop cannot branch, cross itself, or form multiple isolated circuits. It must form exactly one single closed polygon.

4. Every White Cell VisitedEvery cell that is neither a clue nor a black square MUST be traversed by the loop. No dead white squares are permitted!

Master Deductive Tactics

1. Clear Zero Rays First

Any arrow marked with "0" immediately confirms that every cell in that ray direction cannot be black. Because they cannot be black and are not clues, the loop must visit every single one of them.

2. Dead-End & Corner Forcing

When a white cell is located in a grid corner or bordered by clues/walls on two sides, the loop has only two available exits. The loop path through that cell is 100% forced!

3. Black Square Orthogonal Cushion

Whenever you confirm a black square, immediately mark its north, south, east, and west neighbors as white track cells. Since they cannot be black, the loop must travel through them.

4. Early Loop Closure Avoidance

Never connect two loose loop ends if doing so would form a mini-circuit while unvisited white cells still remain on the board. The loop must link every valid cell into one unified journey.

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