This year, we started posting 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 eighth Sunday Stumper is a Hungarian Tapa from puzzlemaster Palmer Mebane.

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

Theme: Four Corners of Four

Author/Opus: This is the 52nd puzzle from our contributing puzzlemaster Palmer Mebane.

Rules: Variation of Tapa. Shade some empty cells black to create a single connected wall. Cells with numbers cannot be shaded, and the shaded cells cannot form a 2×2 square anywhere in the grid. Each row and column must contain eight shaded cells (four for the example). Place a number from 1 to 8 (1-4 for the example) into each shaded cell so that each number appears once in each row and column.

Numbers in a cell indicate the sums of the numbers of consecutive shaded blocks in the neighboring cells. If there is more than one number in a cell, then there must be at least one white (unshaded) cell between the black cell groups. Numbers on the shaded cells can repeat in a sum.

See also this example:

Difficulty: 5 stars

Time Standards (highlight to view): Grandmaster = 35:00, Master = 1:05:00, Expert = 2:10:00

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

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

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the composite Yajilin mode where left click marks cells, right click marks dots in cells or X’s on edges, left click+drag draws lines.)

Theme: Parquet

Author/Opus: This is the 391st puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Tapa rules. Also, the grid is divided into regions by bold lines; exactly five cells must be shaded black in each region.

See also this example:

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 5:45, Master = 11:15, Expert = 22:30

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

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

PDF

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

Theme: Squares

Author/Opus: This is the 51st puzzle from our contributing puzzlemaster Palmer Mebane.

Rules: Standard Statue Park rules, using a standard pentomino set. Also, there are some given cages with dashed lines. In each cage, exactly half of the total number of cells must be occupied by pentominoes.

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 10:00, Master = 16:30, Expert = 33:00

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

Note: Follow this link for other classic Statue Park and this link for Statue Park variations. If you are new to this puzzle type, here are our easiest Statue Parks to get started on. More Statue Park puzzles can be found in the ebook Statue Park by Murat Can Tonta.

PDF

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

Theme: Square Knots

Author/Opus: This is the 2nd puzzle from guest contributor Michael Rios.

Rules: Standard Sudoku rules. Also, some arrow shapes are in the grid; the sum of the digits along the path of each arrow must equal the digit in the circled cell (digits can repeat on an arrow). Some cages are in the grid marked by dashed lines; the sum of the digits in these cages must equal the value given in the upper-left corner of that cage (digits cannot repeat inside a cage). Some dots are given between two cells; a white dot shows that the digits in those cells are consecutive and a black dot shows that the digit in one of the cells has twice the value of the other (adjacent cells without dots may or may not follow these rules). Finally, some thermometer shapes are in the grid; the digits along the thermometer must be strictly increasing from the round bulb to the flat end.

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 10:45, Master = 18:45, Expert = 37:30

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

Note: Follow this link for more Arrow Sudoku. Follow this link for more Thermo-Sudoku puzzles. More Arrow and Thermo-Sudoku puzzles can be found in The Art of Sudoku 2. More Killer Sudoku puzzles can be found in Killer Sudoku by Serkan Yürekli.

PDF

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

Theme: Antisymmetry

Author/Opus: This is the 30th puzzle from our contributing puzzlemaster JinHoo Ahn.

Rules: Standard Arrow Sudoku rules. Also, standard Thermo-Sudoku rules.

Difficulty: 2.5 stars

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

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

Note: Follow this link for more Arrow Sudoku. Follow this link for more Thermo-Sudoku puzzles. More Arrow and Thermo-Sudoku puzzles can be found in The Art of Sudoku 2.

PDF

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: Slanted Squares

Author/Opus: This is the 2nd puzzle from guest contributor Mark Sweep.

Rules: Standard Castle Wall rules, but none of the clue colors are given. The solver should determine whether each gray clue is white or black. Also, the loop must go straight through the cells with white circles, with a turn in at least one of the cells immediately before/after each white circle. The loop must make a turn in all the black circles, but must go straight in both cells immediately before/after each black circle.

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 5:15, Master = 8:00, Expert = 16:00

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

Note: Follow this link for more Castle Wall puzzles. If you are new to this puzzle type, here are our easiest Castle Wall puzzles to get started on. More Castle Wall puzzles can be found in our beginner-friendly collection Intro to GMPuzzles as well as the larger collection Castle Wall, both by Serkan Yürekli.

I was quite saddened to learn that Maki Kaji, founder of the puzzle company Nikoli, passed away last week from cancer. A lot of the news about the “Godfather of Sudoku” will focus on one puzzle, as Nikoli’s renaming of Number Place / Nanpure into “Sudoku” became the inspiration for the global craze. My own note of thanks and remembrance will be broader, about the many many different kinds of puzzles that came out of the community of Nikoli authors and publications that Maki helped to create, starting with the first Puzzle Communication Nikoli in the early 1980s.

I would not have gotten as passionate about logic puzzles if I hadn’t run into Nikoli’s hand-crafted puzzles in the mid 2000s. As I wrote to Maki Kaji back in 2011 about my history with Nikoli, after sharing dinner with him and other puzzle friends in San Francisco:
“I got a Nikoli Communication magazine, #112 I think, when I was at the World Puzzle Championship in 2005 in Eger, Hungary. This was my first international trip to solve puzzles, and my first experience seeing many foreign puzzle sources, but I knew very quickly that Nikoli was special.” I ordered hundreds of books and probably solved tens of thousands of Nikoli puzzles in the decade after first finding a Nikoli magazine. If I could have submitted puzzles to Nikoli, I would have. Nikoli’s set of publications and community building efforts, including a focus on simple, elegant, and visually interesting designs, continues to inspire us at GMPuzzles. We hope to someday influence the puzzle community as much as Maki Kaji did and his company still does.

Here is a Wordoku puzzle I wrote today to remember Maki Kaji:

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

Theme: Rest in Peace, Maki Kaji (1951-2021)

Author/Opus: This is the 389th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Place a letter from A, I, J, K, L, M, N, O, or the symbol ? into each cell so that no character repeats in any row, column, or bold region.

Solution: PDF

This year, we have started to have 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 is a Japanese Sums (Cipher) puzzle with a hidden theme.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between number entry, sudoku, and shading modes. Note that any extra numbers (in green, blue, or red) or shaded cells outside the grid will interfere with solution checking. So we suggest using the Number mode in black to write notes over the outside clues or in the cipher box below the grid; make sure only blue digits are inside the 11×11 grid and not outside the grid.)

Theme: Hidden

Author/Opus: This is the 203rd puzzle from our contributing puzzlemaster Murat Can Tonta.

Rules: Place the digits 1-9 in some of the cells, so that no digit is repeated in any row or column. Also, all numbers are encrypted with J, A, P, N, E, S, U, M, H, D letters and each letter represents a different digit from 0 to 9. Numbers on the outside of the grid indicate the sums of adjacent digit groups in that row or column, in order. Each sum is separated by at least one unused cell. Single-digit clues cannot be a 0, and also multi-digit clues cannot start with a 0. A question mark indicates a sum value of unknown size, and can be single- or multi-digit.

Or see this (non-cipher) example of Japanese Sums:

Difficulty: 5 stars

Time Standards (highlight to view): Grandmaster = 27:30, Master = 37:00, Expert = 1:14:00

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

Note: Follow this link for other Japanese Sums puzzles.

PDF

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

Theme: Poker Face

Author/Opus: This is the 75th puzzle from our contributing puzzlemaster Ashish Kumar.

Rules: Standard Arrow Sudoku rules. Also, some of the digits in the circles are encrypted with letters. Each letter represents a different positive integer, for the solver to determine.

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 7:00, Master = 17:30, Expert = 35:00

Solution: PDF; a solution video 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. More Arrow Sudoku puzzles can be found in The Art of Sudoku 2 and Masterpiece Sudoku Mix 3.

PDF

or solve online (using our beta test of Penpa-Edit tools; note that solution checking requires the 12 ciphered clues and the thirty-six interior cells to all be marked)

Theme: NEWS

Author/Opus: This is the 28th puzzle from our contributing puzzlemaster JinHoo Ahn.

Rules: Standard Skyscrapers rules, using the integers 1-6. Also, each letter represents a different positive integer, for the solver to determine.

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 5:30, Master = 13:30, Expert = 27:00

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

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