How to Solve Yajilin
The rules of yajilin fit in a paragraph. Getting good at it takes practice. This covers the techniques that matter most — the things that actually help you go from staring at a grid to filling it in with confidence.
Quick rules recap
You've got a grid with some arrow clues. Each arrow has a number and points in a direction — that number tells you how many cells to shade in that direction. Shaded cells can't touch each other horizontally or vertically. Every unshaded, non-clue cell must be part of a single continuous loop. No branches, no crossings. That's it.
Start with zero clues
A zero clue means nothing is shaded in that direction. That's free information — every cell in that line is either a clue cell or part of the loop. On bigger grids, zero clues can rule out large chunks of the board immediately. Always process these first.
Edges narrow things down fast
An arrow clue pointing toward a nearby edge has fewer cells to work with. If a clue says 1 and there are only two cells between it and the edge, the shaded cell must be one of those two. If there's only one cell, it must be shaded. Corners are even more constrained — a cell in the corner of the grid only has two possible loop directions, so the loop path there is forced.
The adjacency cascade
This is where yajilin gets interesting. When you shade a cell, all four orthogonal neighbours must be unshaded — they're loop cells. And since they're loop cells, the loop must pass through them, which constrains their neighbours. One shaded cell can resolve a whole chunk of the grid. Work through these implications every time you place a shaded cell.
Forced loop segments
Look for cells that only have two possible loop connections. The loop must enter and exit through exactly those sides. Corridors, corners, and cells next to shaded cells or clue cells often force the loop into specific paths. Drawing these in early gives you more to work with.
Connectivity
The loop is a single connected path through every unshaded non-clue cell. If shading a cell would cut the grid into disconnected regions — where the loop couldn't reach everything — then that cell can't be shaded. This is harder to spot at first but becomes second nature. When you're stuck, ask: would this shade break connectivity?
Practice makes it click
Loopr has over 1,000 yajilin puzzles across three difficulties. Start with Easy to build your intuition, then work up.