What Is Yajilin? Rules, a Worked Example, and Beginner Tactics

What is Yajilin, exactly?

What is Yajilin? It is a two-layer Japanese logic puzzle that asks you to do two jobs at once: shade a handful of cells and draw a single closed loop through everything that is left. The grid holds a few clue cells, each printed with an arrow and a number, and those clues quietly steer the whole solution. Yajilin rewards players who like combining ideas, because it blends the shading logic of puzzles like Hitori with the loop-drawing of puzzles like Slitherlink. Once you understand what the arrows are counting, the board stops looking chaotic and starts feeling like a single connected path waiting to be uncovered. Many Sudoku solvers try Yajilin looking for a fresh challenge and stay for its satisfying, interlocking deductions.

The rules of Yajilin

The rules of Yajilin are precise. Certain cells are clue cells that contain an arrow and a number; that number tells you exactly how many shaded, or black, cells lie in the pointed direction along that same row or column. Clue cells are never shaded and are never part of the loop. Your first task is to shade some of the empty cells so that all the arrow counts are satisfied. Two shaded cells may never share an edge, so no two blacks sit orthogonally next to each other. Your second task is to draw exactly one closed loop that travels only horizontally and vertically through the centers of every remaining empty cell. The loop cannot cross itself, branch, or skip a cell, and it must pass through all cells that are neither shaded nor clues.

Here is a short worked example. Suppose a clue near the top left points to the right and shows the number two. That promises exactly two shaded cells somewhere to its right in that row. Because shaded cells can never touch, those two blacks must have at least one empty cell between them. Now remember that the loop has to visit every non-shaded cell without dead ends. If shading a particular cell would strand a neighbor so the loop could not pass through it cleanly, that cell must stay empty instead. By bouncing between the arrow counts, the no-touching rule, and the need for one unbroken loop, you can pin down which cells are black and how the path must weave around them.

Beginner tactics for Yajilin

• Mark every clue cell as permanently white and off the loop; they only give information, they are never part of the path.
• A clue of zero means there are no shaded cells in that direction, so all of those cells become loop cells right away.
• Use the no-touching rule aggressively; once one black is placed, its four orthogonal neighbors are forced to stay white.
• Look for cells the loop can enter only one way, such as corners and edges, and lock those segments in first.
• Remember every white cell must be visited; a cell that would otherwise be isolated must either be shaded or connected by the loop.

How Yajilin compares to Sudoku

Compared with Sudoku, Yajilin trades symbol placement for construction. In Sudoku you fill a grid so every row, column, and box contains each of nine symbols once, working purely by elimination. Yajilin keeps that guaranteed single solution and guess-free spirit, but you build two things at once, a set of shaded cells and one continuous loop, and each layer constrains the other. If you enjoy tracing a single flowing line to its conclusion, you might also like Rune Flow, a relaxing path game from the studio behind Shapedoku. And if you want to return to the pure every-symbol-once rhythm of Sudoku with a calmer, more mystical look, Shapedoku swaps the usual digits for nine glowing shapes you can read by color and form. Explore the free solver and printable puzzles at shapedoku.com, or play in your browser at app.shapedoku.com.