What is Yajilin?
Yajilin is a Japanese loop and shading logic puzzle. The grid contains arrow clues with numbers. Your job is to shade the right cells and draw one continuous loop through every remaining empty cell.
Each arrow clue tells you how many shaded cells appear in that arrow's direction. Clue cells are never part of the loop, shaded cells cannot touch orthogonally, and the finished loop cannot branch, cross itself, or leave loose ends.
- Follow each arrow clue to count shaded cells in that row or column.
- Do not shade two orthogonally adjacent cells.
- Draw a single closed loop through all unshaded, non-clue cells.
- The loop never passes through clue cells or shaded cells.
- Every board is checked by a solver before you see it, so each puzzle has exactly one solution.
How to play Yajilin online
Click or tap an empty cell to shade it. Click or tap between two neighbouring empty cells to draw a loop segment. A valid answer uses both parts of the puzzle: the arrow clues decide the shaded cells, and the unshaded cells must all belong to one loop.
Use Check when you want feedback without revealing the answer. Hint adds one useful shaded cell or loop segment from the generated solution, and Solution shows the complete board for study.
- Start with arrows that point along short lines.
- A clue showing 0 means every cell in that direction is unshaded.
- A clue whose number matches the available spaces can force shaded cells.
- Once a cell is shaded, keep its orthogonal neighbours unshaded.
- When the shaded cells are settled, the loop often has forced exits.
Yajilin grid sizes and difficulty
Smaller Yajilin grids are good for learning how arrows and shaded cells interact. Larger Yajilin boards create longer loops and more distant clue chains.
Easy puzzles use more direct clue pressure and fewer shaded cells. Medium puzzles give more space to reason. Hard Yajilin puzzles use bigger grids, more shaded cells, and longer consequences from a single arrow.
- 6x6 Yajilin is a friendly first size.
- 8x8 Yajilin gives a balanced logic challenge.
- 10x10 Yajilin creates longer loop deductions.
- Easy, medium and hard change the shaded-cell density and clue pressure.
- New puzzle builds another board for the selected size and difficulty.
Yajilin strategy tips
The best Yajilin strategy is to separate the puzzle into two questions. First, decide which cells must be shaded or unshaded from the arrow clues. Then use loop logic to connect every remaining empty cell.
Avoid guessing around the loop too early. A shaded cell removes a square from the loop, but it also forces neighbouring cells to stay open. Those open cells often become part of a narrow corridor with only one possible way through.
- Use 0 clues to mark safe loop cells.
- Compare two arrows that look down the same row or column.
- Watch for shaded cells that would touch another shaded cell.
- Do not close a small loop before every open cell is included.
- Cells with one line already usually need exactly one more exit.
Reading the arrow clues exactly
Each arrow clue counts the shaded cells along the line it points to, all the way to the edge. The trick is to turn that count into placements. Because shaded cells can never touch, fitting N shaded cells into a run needs at least N − 1 gaps between them, so the run has to be at least 2N − 1 cells long. If a clue's number is large for the space available, the shaded cells are squeezed into an almost-fixed alternating pattern.
A clue of 0 is the most powerful of all: it makes every cell in that direction unshaded, which immediately hands them to the loop. At the other extreme, when a clue demands the most a run can hold, the shaded cells must alternate from a forced starting cell. Compare two arrows that scan the same row or column from opposite ends to pin the shaded cells between them.
- An arrow counts shaded cells in its direction, out to the edge.
- N shaded cells need a run of at least 2N − 1 cells to fit without touching.
- A 0 clue makes its whole direction unshaded — instant loop cells.
- A near-maximum clue forces an alternating shaded pattern.
- Cross-check arrows pointing along the same line from both sides.
A worked Yajilin step
Watch how one clue cascades. Suppose an arrow reads 0: every cell in that direction is unshaded, so the loop must pass through all of them. Now suppose a different clue forces a shaded cell nearby. Immediately its four orthogonal neighbours must stay unshaded, because shaded cells cannot touch, and each of those neighbours is therefore a loop cell.
The loop side then takes over. Every unshaded, non-clue cell must lie on the single loop, so it needs exactly two connections. A loop cell against the board edge or beside a shaded cell loses possible directions, and when only two remain, both are forced. One shaded cell can set off a chain of forced turns that snakes across half the grid.
- A 0 clue fills its line with loop cells.
- A shaded cell forces all four neighbours to be unshaded loop cells.
- Every loop cell needs exactly two connections.
- Edges and shaded cells remove possible loop directions.
- When a cell has two directions left, both are forced.
Yajilin, Nikoli and loop puzzles
Yajilin is a Nikoli puzzle, from the Japanese publisher behind Sudoku, Nurikabe and Slitherlink. Its name comes from yajirushi, the Japanese word for arrow, joined with 'rin' for link — fitting for a puzzle where arrow clues steer a single linked loop. You may also see it written Yajirin.
It belongs to Nikoli's family of loop puzzles alongside Slitherlink and Masyu, but it adds a shading layer the others do not have. Like its siblings, a classic Yajilin is built for one logical solution. The version here keeps the arrow, shading and single-loop rules and offers 6x6 to 10x10 boards, so you can learn the two-layer logic on a small grid and work up.