Since 2021, we have posted some extra difficult Sunday Stumpers, about once a month. These will be quite tough puzzles, but with a logical path to be found (and solution videos to help). This seventh Sunday Stumper of 2022 is a variation of Japanese Sums by John Bulten.

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or solve online (using our beta test of Penpa-Edit tools; use tab to shift between number entry and shading modes.)

Theme: Yamato

Author/Opus: This is the 88th puzzle from our contributing puzzlemaster John Bulten.

Rules: Standard Japanese Sums rules: Place the numbers in the indicated range (1-9) in some of the cells so that no number is repeated in any row or column. Numbers on the outside of the grid indicate the sums of adjacent number groups in that row or column, in order. Each sum is separated by at least one unused cell. A ? can represent any sum of 1 or larger.

Also, all unused cells must form an unknown fleet of 1-cell wide ships in the grid. Each segment of a ship occupies a single cell, and ships do not touch each other, even diagonally.

Difficulty: 5 stars

Time Standards (highlight to view): Grandmaster = 18:30, Master = 30:00, Expert = 1:00:00

Solution: PDF and solving video.

Note: Follow this link for other Japanese Sums puzzles.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between number entry and shading modes.)

Theme: 1 to 10

Author/Opus: This is the 372nd puzzle from our managing editor Serkan Yürekli.

Rules: Fill some cells with numbers 1-4 so that each row and column contains each number from 1 to 4 exactly once as well as two empty cells. Numbers outside of the grid indicate the sum of all numbers in the first connected group in that direction as in a Japanese Sums puzzle.

Difficulty: 2.5 stars

Time Standards (highlight to view): Grandmaster = 2:00, Master = 3:15, Expert = 6:30

Solution: PDF and solving video.

Note: Follow this link for other Japanese Sums puzzles.

(view directly for a larger image)

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or solve online (using our beta test of Penpa-Edit tools in linex mode where left click+drag draws lines and right click marks X’s)

Theme: Diamonds

Author/Opus: This is the 237th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: Standard Balance Loop rules. Also, number clues are not fully specified and must strictly follow the inequality values given.

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 9:00, Master = 16:00, Expert = 32:00

Solution: PDF and solving video.

Note: Follow this link for other Balance Loop puzzles. If you are new to this puzzle type, here are our easiest Balance Loop Puzzles to get started on. More Balance Loops can be found in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli and in Balance Loop by Prasanna Seshadri and Murat Can Tonta.

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or solve online (using our beta test of Penpa-Edit tools in linex mode where left click+drag draws lines and right click marks X’s)

Author/Opus: This is the 371st puzzle from our managing editor Serkan Yürekli.

Rules: Variation of Balance Loop rules. Each circle clue has either an incorrect color or an incorrect number. If the color is incorrect, the real clue should have the opposite color. If the number is incorrect, the real clue should have a number one more or one less than the given number.

Difficulty: 3 stars

Time Standards (highlight to view): Grandmaster = 3:00, Master = 4:45, Expert = 9:30

Solution: PDF and solving video.

Note: Follow this link for other Balance Loop puzzles. If you are new to this puzzle type, here are our easiest Balance Loop Puzzles to get started on. More Balance Loops can be found in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli and in Balance Loop by Prasanna Seshadri and Murat Can Tonta.

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or solve online (using our beta test of Penpa-Edit tools in linex mode where left click+drag draws lines and right click marks X’s)

Theme: BALANCE

Author/Opus: This is the 22nd puzzle from guest contributor Bryce Herdt.

Rules: Variation of Balance Loop rules. (Draw a single, non-intersecting loop that passes through all circled cells. All white circles must have equal segment lengths on both sides of the circle before turning. All black circles must have unequal segment lengths on both sides of the circle before turning.)

Numbers, where given, indicate the length of only one of the two loop segments coming out from the circle. All other rules for the loop are the same as usual.

Difficulty: 1 star

Time Standards (highlight to view): Grandmaster = 0:50, Master = 1:15, Expert = 2:30

Solution: PDF and solving video.

Note: Follow this link for other Balance Loop puzzles. If you are new to this puzzle type, here are our easiest Balance Loop Puzzles to get started on. More Balance Loops can be found in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli and in Balance Loop by Prasanna Seshadri and Murat Can Tonta.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between a composite mode for line/edge drawing and a number entry mode.)

Theme: Series

Author/Opus: This is the 30th puzzle from guest contributor Joseph Howard.

Rules: (Hybrid of Fillomino and Snake Puzzles.) Divide the grid along the boundary lines so that every cell belongs to a snake. A snake is a one-cell-wide path at least two cells long that does not touch itself, not even diagonally. Circled cells must be at one of the ends of a snake. A snake may contain one circled cell, two circled cells, or no circled cells at all. Numbered cells must be part of a snake with a length of exactly that number of cells. A snake may contain one number, multiple identical numbers, or no numbers at all. Two snakes of the same length cannot touch each other horizontally or vertically. Cells with an X cannot be an end of a snake.

Also see this example:

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 9:00, Master = 16:00, Expert = 32:00

Solution: PDF and solving video.

Note: Follow this link for more Snake Pit puzzles. Follow these links for other Fillomino or Snake puzzles.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between a composite mode for line/edge drawing and a number entry mode.)

Theme: Surrounded

Author/Opus: This is the 236th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: (Hybrid of Fillomino and Snake Puzzles.) Divide the grid along the boundary lines so that every cell belongs to a snake. A snake is a one-cell-wide path at least two cells long that does not touch itself, not even diagonally. Circled cells must be at one of the ends of a snake. A snake may contain one circled cell, two circled cells, or no circled cells at all. Numbered cells must be part of a snake with a length of exactly that number of cells. A snake may contain one number, multiple identical numbers, or no numbers at all. Two snakes of the same length cannot touch each other horizontally or vertically. Cells with an X cannot be an end of a snake.

Also see this example:

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 6:00, Master = 8:30, Expert = 17:00

Solution: PDF and solving video.

Note: Follow this link for more Snake Pit puzzles. Follow these links for other Fillomino or Snake puzzles.

(view directly for a larger image)

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between a composite mode for line/edge drawing, a shading mode for ships, and a letter entry mode.)

Author/Opus: This is the 377th puzzle from our contributing puzzlemaster Grant Fikes.

Rules: Combination of Pentominous and Battleships. Locate the indicated fleet in the grid. Each segment of a ship occupies a single cell. Ships can be rotated. Different ships cannot be placed in adjacent cells that share an edge or corner. Then divide the rest of the grid into 16 regions each containing 5 cells. Regions with the same shape (including rotations/reflections) cannot share an edge. A cell with a letter in it must be part of the pentomino shape normally associated with that letter; an inventory of pentominoes is given below the puzzle.

Difficulty: 3 stars

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

Solution: PDF and solving video.

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.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between ship placement and shading modes. In ship placement mode, right click gives sea, left click gives circle/square, left click and drag for rounded ships.)

Theme: Question Mark

Author/Opus: This is the 3rd puzzle from guest contributor Hatice Esra Aydemir.

Rules: Variation of standard Battleships rules. Instead of exterior clues, clues inside the grid indicate the number of adjacent squares, including diagonally adjacent squares, containing ship segments. Ships do not sit on cells with numbers. Use the indicated fleet.

Difficulty: 2.5 stars

Time Standards (highlight to view): Grandmaster = 2:30, Master = 4:00, Expert = 8:00

Solution: PDF and solving video.

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.

PDF

or solve online (using our beta test of Penpa-Edit tools in edgex mode where left click+drag draws lines and right click marks X’s)

Theme: Snowflake

Author/Opus: This is the 414th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Slitherlink rules (with a hexagonal grid).

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 11:00, Master = 16:00, Expert = 32:00

Solution: PDF and solving video.

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