This is a bonus Sunday puzzle for Valentine’s Day, and one more puzzle to conclude a full week of puzzles from JinHoo Ahn.

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

Theme: Valentine

Author/Opus: This is the 18th puzzle from our contributing puzzlemaster JinHoo Ahn.

Rules: Standard Masyu rules. Also, some white circles may be shaded to become black circles. (Stylistically, here the white circles are white with red borders and the black circles are filled, red circles.)

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 3:30, Master = 8:00, Expert = 16:00

Solution: PDF

Note: Follow this link for other Masyu variations and this link for classic Masyu. If you are new to this puzzle type, here are our easiest Masyu to get started on. More Masyu puzzles can be found in The Art of Puzzles.

We hope you enjoyed JinHoo Ahn’s debut week as a new puzzlemaster on GMPuzzles. You can find the six puzzle variations in this PDF and the solutions for each variation in this PDF. Like all our debut weeks, there was something extra going on here in each of the puzzles from Monday to Saturday. If you haven’t found anything special yet, keep looking, or read through these hints:

1. Find something in common between the six puzzles
2. What if what was most in common was ignored?
3. The week features six variations on puzzles, but you may be able to solve them another way.
4. Remove all of the instructions after the phrase “Instead of their usual meaning”. These puzzles all double as classic versions of the same style.

Solving videos for the six puzzles are below. All of the videos include info on the Easter Eggs for the week in the second part of each video, so if you want to avoid spoilers you should be prepared to pause the video at the spoiler warning:

We will have one more bonus puzzle from JinHoo for Valentine’s Day, posting very soon (it does not have an extra Easter Egg). This coming week features Star Battle puzzles, which was the genre for JinHoo Ahn’s first book with us.

PDF

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

Theme: Groups

Author/Opus: This is the 17th puzzle from our new contributing puzzlemaster JinHoo Ahn.

Rules: Variation of Cross the Streams rules. Instead of their usual meaning, clues refer to the distribution of the white cells. The shaded cells must still obey the regular rules (connectivity, no 2×2 squares).

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 6:30, Master = 10:30, Expert = 21:00

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

Note: Follow this link for other Cross the Streams. If you are new to this puzzle type, here are our easiest Cross the Streams to get started on.

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:

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.

PDF

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

Theme: Knight Steps

Author/Opus: This is the 15th puzzle from our new contributing puzzlemaster JinHoo Ahn.

Rules: Variation of Cave rules. Instead of their usual meaning, interior clues indicate the number of shaded cells in neighboring cells, including diagonally adjacent cells. Cells with numbers cannot be shaded.

See also this example:

Difficulty: 3 stars

Time Standards (highlight to view): Grandmaster = 4:00, Master = 5:15, Expert = 10:30

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

Note: Follow this link for other classic Caves and this link for Cave variations. If you are new to this puzzle type, here are our easiest Cave Puzzles to get started on. More Cave puzzles can be found in Roger Barkan’s Colossal Cave Collection, in The Art of Puzzles, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

PDF

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

Theme: Double X

Author/Opus: This is the 14th puzzle from our new contributing puzzlemaster JinHoo Ahn.

Rules: Variation of Arrow Sudoku rules. Instead of the usual meaning, the digit in the circled cell of each arrow must equal the product of the digits along the path.

Difficulty: 3 stars

Time Standards (highlight to view): Grandmaster = 3:30, Master = 4:45, Expert = 9:30

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

Note: Follow this link for more Arrow Sudoku. If you are new to this puzzle type, here are our easiest Arrow Sudoku to get started on.

PDF

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

Theme: Rise and Fall

Author/Opus: This is the 13th puzzle from our new contributing puzzlemaster JinHoo Ahn.

Rules: Variation of Battleships rules. Instead of their usual meaning, exterior clues indicate the length of the first ship seen from the corresponding direction.

See also this example:

Difficulty: 2 stars

Time Standards (highlight to view): Grandmaster = 2:00, Master = 3:00, Expert = 6:00

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

Note: Follow this link for classic Battleships and this link for Battleships variations. If you are new to this puzzle type, here are our easiest Battleships to get started on. More Battleships puzzles can be found in Battleships and Variations, in The Art of Puzzles, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.