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:

PDF

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.

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.

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 letter entry mode.)

Theme: Box in Box

Author/Opus: This is the 8th puzzle from guest contributor Takeya Saikachi.

Rules: Variation of Pentominous rules. Divide the grid into 20 pentominoes so that no two pentominoes of the same shape (including rotations/reflections) share an edge. Each number in this grid represents a clue for a different letter/pentomino as in a regular Pentominous puzzle; all instances of a number must represent the same letter. An inventory of possible pentominoes is given below the puzzle.

Difficulty: 3 stars

Time Standards (highlight to view): Grandmaster = 3:30, Master = 5:00, Expert = 10:00

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

Note: Follow this link for other Pentominous puzzles. If you are new to this puzzle type, here are our easiest Pentominous to get started on. More Pentominous puzzles can be found in the Plenty o’ Pentominous series by Grant Fikes and Murat Can Tonta 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 shading and number placement modes.)

Theme: GMP! WOW WOW!

Author/Opus: This is the 212th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: Standard Tapa rules, except that the digits have been encoded with a cipher into letters. Each letter represents a different positive integer, for the solver to determine.

Difficulty: 2 stars

Time Standards (highlight to view): Grandmaster = 1:45, Master = 3:15, Expert = 6:30

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; use tab to alternate between ship placement, shading, and number placement modes. In ship placement mode, right click gives sea, left click gives circle/square, left click and drag for rounded ships.)

Theme: BATTLE

Author/Opus: This is the 336th puzzle from our managing editor Serkan Yürekli.

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

Difficulty: 1.5 stars

Time Standards (highlight to view): Grandmaster = 1:30, Master = 2:00, Expert = 4:00

Solution: PDF; a solution video 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.

PDF

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

Theme: Doppel

Author/Opus: This is the 202nd puzzle from our contributing puzzlemaster Murat Can Tonta.

Rules: Fill each row and column of the grid with the digits 1 to 5 and two blackened cells. Numbers outside the grid indicate the sum of the digits between the two blackened cells in that row or column. Blackened cells are allowed to touch. Or see here.

Difficulty: 2.5 stars

Time Standards (highlight to view): Grandmaster = 2:45, Master = 3:30, Expert = 7:00

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

Note: Follow this link for other less common Number Placement puzzles.

PDF

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

Theme: For 08/03/21

Author/Opus: This is the 388th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Fill each row and column of the grid with the digits 1 to 4 and two blackened cells. Numbers outside the grid indicate the sum of the digits between the two blackened cells in that row or column. Blackened cells are allowed to touch. Or see here.

Difficulty: 2 stars

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

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

Note: Follow this link for other less common Number Placement puzzles.