Play Yajilin Online Free

Yajilin first appeared in Nikoli issue 86 in June 1999. Arrow clues state how many black cells lie in one direction, while the remaining usable cells must carry a single closed loop. Black cells cannot share an edge, and the loop cannot branch or cross. Solvers switch between counting, route construction, and parity reasoning, so each mark can affect two different systems. Read an arrow, identify the cells it governs, and draw your first safe loop segment in the browser.

1. Read each clue cell as an arrow plus a number. Count exactly that many black cells anywhere along the indicated row or column beyond the arrow. The clue cell itself never joins the loop and never becomes black.
2. Mark forced black cells and excluded cells from arrow counts. If a clue already sees its required number of black cells, every other candidate in its direction must remain nonblack. If all remaining candidates are needed, shade all of them.
3. Apply black separation immediately. Orthogonally adjacent cells cannot both be black, so mark every edge-neighbor of a black cell as nonblack. Those usable non-clue cells must eventually carry loop segments.
4. Draw loop segments so every loop cell has degree two. Continue a path when a cell already has one segment and only one legal exit. Never create a branch, crossing, or small closed circuit while unused loop cells remain.
5. Finish with one continuous closed loop through every cell that is neither a clue nor black. Verify all arrow counts, black separation, and cell degrees before joining the final two endpoints.

• Clue cells stay outside the loop and cannot become black. Their arrows count black cells in the indicated direction up to the grid edge.
• Black cells cannot share an edge. They may touch diagonally, and the loop travels through their orthogonal neighbors when those cells are not clues.
• Every non-clue cell that is not black belongs to the loop. The path enters and leaves each such cell exactly once, giving it two incident segments.
• The loop uses horizontal and vertical connections, never crosses itself, and never branches. It must form one closed component rather than several separate cycles.
• Arrow clues count all black cells across their full sight line rather than a single consecutive group. Clue cells or loop cells between the arrow and a black cell do not block the count.

• Use clue saturation in both directions. When an arrow has found all required black cells, mark every other target cell nonblack. When the number of undecided legal targets equals the residual count, shade them all.
• Translate black adjacency into loop obligations. The four edge-neighbors of a black cell cannot be black, and any that are not clue cells must join the loop. Check their available entrances before placing the next black cell nearby.
• Avoid premature cycles. If connecting two endpoints would close a loop while another usable cell remains outside, forbid that edge. The final connection should occur only after the path includes every required cell.
• Watch bottlenecks and degree. A usable cell with exactly two available neighboring cells must connect to both. A cell that already has two segments rejects every other edge, often forcing turns in adjacent cells.
• Apply parity along constrained strips. A narrow corridor of usable cells may require alternating turns or connections. Test how its two endpoints can join the wider route, and reject an arrangement that leaves an odd stranded endpoint.

• Kurodoko: Kurodoko shares the ban on edge-adjacent black cells, but its numbers measure white visibility and its white cells form an area rather than a loop. The comparison highlights how one shading rule supports different goals.
• Slitherlink: Slitherlink also builds one noncrossing loop, usually along cell edges according to local number clues. Yajilin routes through cell centers and combines the path with directional black-cell counts.

• Shading and routing continually exchange information. An arrow can force a black cell, which forces neighboring loop cells, which can then rule out another black candidate.
• The single-loop condition creates clear tactical moments. Solvers must connect local segments while resisting an early cycle, so the final join feels earned.
• Arrow sight lines vary in length and direction. Short clues produce immediate counts, while long clues coordinate distant parts of the route and sustain deductions across the board.

Play Yajilin online for free with arrow counts, black-cell marks, and loop drawing in one responsive grid. Click or drag to add route segments, mark excluded edges, and revise a turn when it would close too soon. The interface checks geometry while you focus on deductions. Begin with a small board, saturate a short arrow clue, and follow the forced usable cells into the emerging loop.

Yajilin joined Nikoli in issue 86 in June 1999 and remains distinctive because every solve combines a counting puzzle with a route puzzle. Satisfy each arrow, separate black cells, give every usable cell two connections, and close only one loop. When progress slows, move information from one system to the other. Start above, resolve a clue with few candidates, and trace the consequences until the final endpoints meet.

• Yajilin rules (Nikoli)