Yajilin (Castle Wall) by Thomas Snyder

See more discussion of the puzzles from the United States’ 2021 Puzzle Grand Prix on this post. Note there are some construction details and potential spoilers on that post so view it after you solve.

Yajilin (Castle Wall) by Thomas Snyder

PDF

or solve online (using our beta test of Penpa-Edit tools using a composite mode where left click inside cell shades square, left click + drag draws line segment, right click inside cell adds dot, and right click on cell edge adds an x.)

Author/Opus: This is the 401st* puzzle from Thomas Snyder, aka Dr. Sudoku (*the 400th puzzle opus number is being held for an upcoming post).

Rules: Standard Yajilin rules: Blacken some white cells and then draw a single closed loop (without intersections or crossings) through all remaining white cells. Blackened cells cannot share an edge with each other. Some cells are outlined and in gray and cannot be part of the loop. Numbered arrows in such cells indicate the total number of blackened cells that exist in that direction in the grid.

Also, in addition to the usual gray clues, some clues are white and black and act similarly to Castle Wall clues. White clues must be inside the loop and black clues must be outside the loop. White and black clues indicate the sum of the lengths of loop segments in the indicated direction.

Difficulty: 2.5 stars (estimate based off competition points; timing standards not available from our usual testers)

Solution: PDF

Note: Follow this link for classic Yajilin and this link for Yajilin variations. Follow this link for more Castle Wall puzzles.

Yajilin (Cipher) by Carl Worth

Yajilin (Cipher) by Carl Worth

PDF

or solve online (using our beta test of Penpa-Edit tools)

Theme: Lots of Laughs

Author/Opus: This is the 38th puzzle from our contributing puzzlemaster Carl Worth.

Rules: Standard Yajilin rules. Also, the letters A, E, H, L, O represent different digits from 0-9. Identify which letters stand for which digits and then solve the Yajilin.

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 3:45, Master = 8:30, Expert = 17:00

Solution: PDF; a solution video is also available here.

Note: Follow this link for classic Yajilin and this link for Yajilin variations. If you are new to this puzzle type, here are our easiest Yajilin to get started on. More Yajilin puzzles can be found in The Art of Puzzles 2, in Yajilin by Murat Can Tonta and Prasanna Seshadri, and in our beginner-friendly book Logic Puzzles 101.

Yajilin (One Of) by Serkan Yürekli

Yajilin by Serkan Yürekli

PDF

or solve online (using our beta test of Penpa-Edit tools; tab key alternates between Yajilin solving tool and a gray arrow mode which can be used to mark over some of the clues)

Theme: Stretching the Circle

Author/Opus: This is the 329th puzzle from our managing editor Serkan Yürekli.

Rules: Variation of Yajilin rules. Numbers indicate the total number of blackened cells in one of the two directions pointed to by arrows. Numbers do not give any information about the other direction indicated by the arrows.

Difficulty: 3 stars

Time Standards (highlight to view): Grandmaster = 3:15, Master = 5:15, Expert = 10:30

Solution: PDF; a solution video is also available here.

Note: Follow this link for classic Yajilin and this link for Yajilin variations. If you are new to this puzzle type, here are our easiest Yajilin to get started on. More Yajilin puzzles can be found in The Art of Puzzles 2, in Yajilin by Murat Can Tonta and Prasanna Seshadri, and in our beginner-friendly book Logic Puzzles 101.

Yajilin (Even Rows/Columns) by Ashish Kumar

Yajilin by Ashish Kumar

PDF

or solve online (using our beta test of Penpa-Edit tools)

Theme: Target One

Author/Opus: This is the 61st puzzle from our contributing puzzlemaster Ashish Kumar.

Rules: Standard Yajilin rules. Also, an even number of cells must be shaded in each row and in each column.

Difficulty: 2 stars

Time Standards (highlight to view): Grandmaster = 1:15, Master = 2:00, Expert = 4:00

Solution: PDF; a solution video is also available here.

Note: Follow this link for classic Yajilin and this link for Yajilin variations. If you are new to this puzzle type, here are our easiest Yajilin to get started on. More Yajilin puzzles can be found in The Art of Puzzles 2, in Yajilin by Murat Can Tonta and Prasanna Seshadri, and in our beginner-friendly book Logic Puzzles 101.

Contest Puzzle: Linking 200 Cells by Prasanna Seshadri

Prasanna is celebrating two milestones this week and we will have two special large puzzles. The first one here recognizes Prasanna’s 200th submission on GMPuzzles, and combines three of the styles where Prasanna has written books for our e-store.

Puzzle by Prasanna Seshadri

(view directly for a larger image)

PDF

or solve online (using our beta test of Penpa-Edit tools; while solution checking is not enabled, if you are comfortable with the different tool selection options you should be able to fully solve the puzzle in this mode too.)

Theme: Linking 200 cells

Author/Opus: This is the 200th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules:

Grids 1-2: Follow regular LITS rules. Between the two LITS grids, the corresponding white cells can never both be shaded, while the corresponding gray cells must be identical in the three 200-shaped regions.

Use the LITS solutions and your ingenuity to discover the needed constraints for Grids 3-4. For Grid 3, you will find that some gray circles must change color to white or black.

Grid 3: Follow regular Balance Loop rules. Additionally, the loop must cross itself if it passes through a gray circle. The loop must go straight throught the gray circle both times; in one direction the path behaves as if the circle is white with equal loop lengths, and in the other direction the path behaves as if the circle is black with unequal loop lengths. It is not required that the loop pass through all of the gray circles (but it must pass through all white and black circles). (See also the image below.)

Grid 4: Follow regular Yajilin rules.

When taken together, the grids yield a short final answer! Send this (less than five character) string to hiddencontest at gmpuzzles dot com by March 14th, 2021 to be eligible to win an e-book by Prasanna Seshadri. The contest is now closed and results summarized here.

Difficulty: 5 stars?

Solution: PDF

Yajilin (Castle Wall) by JinHoo Ahn

Yajilin (Castle Wall) by JinHoo Ahn

PDF

or solve online (using our beta test of Penpa-Edit tools)

Theme: Open Middle

Author/Opus: This is the 16th puzzle from our new contributing puzzlemaster JinHoo Ahn.

Rules: Variation of Yajilin rules. Instead of their usual meaning, interior clues refer to the total sum of the lengths of loop segments in the given direction. (An equivalent way to understand these values is to count the number of cell borders crossed by the loop in that direction.)

See also this example:

Yajilin (Castle Wall) example by Serkan Yürekli

Difficulty: 3 stars

Time Standards (highlight to view): Grandmaster = 3:15, Master = 6:00, Expert = 12:00

Solution: PDF; a solution video (with info on an Easter Egg for this puzzle) is also available here.

Note: Follow this link for classic Yajilin and this link for Yajilin variations. If you are new to this puzzle type, here are our easiest Yajilin to get started on. More Yajilin puzzles can be found in The Art of Puzzles 2, in Yajilin by Murat Can Tonta and Prasanna Seshadri, and in our beginner-friendly book Logic Puzzles 101.

E-book and Bonus Puzzle: Yajilin Battleships by Serkan Yürekli

Yajilin and Battleships are two of our favorite Loop and Object Placement puzzles, respectively. What happens when you combine them? Our new e-book Yajilin Battleships by Serkan Yürekli will show you.

We’ve included here the example puzzle from the book which is now available for purchase. We have a companion solving video if you want to see what these puzzles are sometimes like. Some other prior posts with this style from Serkan, Freddie Hand and Grant Fikes are linked.

Yajilin Battleships by Serkan Yürekli

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between Battleships placement and line drawing modes.)

Rules: Variation of Battleships and Yajilin. Place the fleet of ships in the grid so that different ships are not in adjacent cells that share an edge or corner. The grid contains internal clues (a number and an arrow) that show how many ship segments are in the indicated direction. All remaining white cells that do not contain a ship segment must be able to form a single loop, as in a Yajilin puzzle.

Solution: PDF; a solution video is also available here.