Yajilin facts for kids

An example of a Yajilin puzzle.

Solved.

Yajilin (ヤジリン) is a cool type of logic puzzle that comes from Japan. It was created by a well-known puzzle company called Nikoli. You might have also seen it called Arrow Ring in some places, like in a big puzzle competition in the United States back in 2005.

How to Play Yajilin

Yajilin puzzles are played on a grid of squares, a bit like a chessboard. When you start, some squares already have things in them. Other squares are empty. Your job is to figure out which empty squares become black and how to draw a special loop.

Understanding the Grid

The grid has different types of squares:

• Indicative squares: These squares have a number and an arrow inside them. The arrow points either up, down, left, or right. These squares give you clues!
• Empty squares: These squares are blank when you start. You'll need to decide if they become part of your loop or turn black.
• Black squares: You'll discover these as you solve the puzzle. They are important for the clues.

Drawing the Loop

Your main goal is to draw a single, continuous line that forms a loop. This loop must go through every square that is not an indicative square and is not a black square.

Here are the rules for drawing your loop:

• The loop must not cross itself. It's like a single path that never touches itself.
• When the loop enters a square, it must come from the center of one of its four sides.
• When the loop leaves a square, it must exit from a different side.
• All turns the loop makes must be 90 degrees (a perfect corner).

What Do the Numbers Mean?

The indicative squares are your helpers! The number inside an indicative square tells you how many black squares are in that row or column, in the direction the arrow is pointing.

For example:

• If an indicative square has a '3' and an arrow pointing left, it means there must be exactly three black squares to the left of that square in the same row.
• Indicative squares themselves can never be black.
• They also don't count as black squares for other indicative squares. The loop cannot pass through them either.

Rules for Black Cells

Black cells are a key part of solving Yajilin. Here's what you need to know about them:

• Black cells cannot touch each other side-by-side. They can touch diagonally, but never sharing a wall. This is called not touching orthogonally.
• Every square that is not an indicative square must either be black or have a part of your loop going through it. There are no "empty" squares left at the end.
• Sometimes, there might be black squares that aren't counted by any indicative cells. That's okay! The important thing is that all indicative cells are correct.

Checking Your Solution

Once you think you've solved a Yajilin puzzle, you can check it by making sure these things are true:

• Did you draw a single, continuous loop that doesn't cross itself?
• Does the loop go through all the non-indicative, non-black squares?
• Are all the indicative cells accurate? Do their numbers match the black cells in the arrow's direction?
• Do none of your black cells touch each other side-by-side?

If all these rules are followed, congratulations, you've solved the Yajilin puzzle!