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Theme: Either/Or

Author/Opus: This is the 552nd puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Fill each cell with an X or O so that (A) no vertical or horizontal group of three adjacent cells contains the same symbol in all cells (i.e., no XXX or OOO) and (B) each row and column contains an equal number of each symbol. Cells separated by an equals sign (=) must contain the same symbol. Cells separated by a cross (×) must contain different symbols.

Solution: PDF and selected animation.

Note: Follow this link for other Number Placement puzzles.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Thirteen Days of Tango Discussion post on the GMPuzzles Discord.

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

Theme: The Eight Tees

Author/Opus: This is the 551st puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Fill each cell with an X or O so that (A) no vertical or horizontal group of three adjacent cells contains the same symbol in all cells (i.e., no XXX or OOO) and (B) each row and column contains an equal number of each symbol. Cells separated by an equals sign (=) must contain the same symbol. Cells separated by a cross (×) must contain different symbols.

Solution: PDF and selected animation.

Note: Follow this link for other Number Placement puzzles.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Thirteen Days of Tango Discussion post on the GMPuzzles Discord.

PDF

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

Theme: Open Middle

Author/Opus: This is the 550th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Fill each cell with an X or O so that (A) no vertical or horizontal group of three adjacent cells contains the same symbol in all cells (i.e., no XXX or OOO) and (B) each row and column contains an equal number of each symbol. Cells separated by an equals sign (=) must contain the same symbol. Cells separated by a cross (×) must contain different symbols.

Solution: PDF and selected animation.

Note: Follow this link for other Number Placement puzzles.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Thirteen Days of Tango Discussion post on the GMPuzzles Discord.

PDF

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

Theme: Stripes

Author/Opus: This is the 549th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Fill each cell with an X or O so that (A) no vertical or horizontal group of three adjacent cells contains the same symbol in all cells (i.e., no XXX or OOO) and (B) each row and column contains an equal number of each symbol. Cells separated by an equals sign (=) must contain the same symbol. Cells separated by a cross (×) must contain different symbols.

Solution: PDF and selected animation.

Note: Follow this link for other Number Placement puzzles.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Thirteen Days of Tango Discussion post on the GMPuzzles Discord.

PDF

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

Theme: Clued Descending a Staircase

Author/Opus: This is the 548th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Sudoku rules.

Time Standards (highlight to view): Grandmaster = 6:15, Master = 9:15, Expert = 18:30

Solution: PDF and solving animation.

Note: Follow this link for other classic Sudoku. If you are new to this puzzle type, here are our easiest Sudoku to get started on. More Sudoku including variations can be found in these books in our e-store. Also, visit this page to purchase all of the puzzles from the 16th World Sudoku Championship including classic Sudoku.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Twelve Days of Sudoku Discussion post on the GMPuzzles Discord.

Note 3: Please check lesson notes from Dr. Sudoku on Google Docs.

Note 4: Thanks to Tyler Hinman for suggesting this playful title long ago for another puzzle (unused then but adopted here).

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Theme: Two Cool

Author/Opus: This is the 547th (A), 547th (B) puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: One of these grids obeys standard Sudoku rules with a unique solution. Solve the Sudoku. The other grid is a Just One Cell Sudoku. This grid has many, many solutions, with only one empty cell that is fixed to one value in all solutions. Find that cell’s location and value.

Time Standards (highlight to view): Grandmaster = 6:15, Master = 13:30, Expert = 27:00

Solution: PDF and solving animation.

Note: Follow this link for other classic Sudoku. If you are new to this puzzle type, here are our easiest Sudoku to get started on. More Sudoku including variations can be found in these books in our e-store. Also, visit this page to purchase all of the puzzles from the 16th World Sudoku Championship including classic Sudoku.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Twelve Days of Sudoku Discussion post on the GMPuzzles Discord.

Note 3: Please check lesson notes from Dr. Sudoku on Google Docs.

PDF

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

Now that we’re approaching the end of the Twelve Days of Sudoku, I’m sure everyone is curious what went on / is going on / will go on with these puzzles. If I had not stopped blogging my thoughts (when I ended my livejournal) and continued thoughts + puzzles, would this amount of raw Snyder have felt less overwhelming? I consider the collected works in these last two weeks my best stuff in puzzles+creativity over the last decade, even if that required exposing more personal things in the making and doing that not everyone in the audience is ready to talk about yet.

For today’s extra post, we start with just a sketch of a fully completed but very weird puzzle idea like the Christmas Miracle I’d posted before the trip. I made this on the flights back to seeing my father in my childhood home, when watching Little Women on the in-flight screen was a bit too boring although something I knew I was supposed to do. If looking for places to start that should get you going with this puzzle series, consider standard puzzles, notes documents, motivational things. Ready Layer One on its own has two answers and with other content at least one more. No one has found any of those. For sure, do not start with this demotivational poster. At least until I digitize it properly. Even then, here is a Knowledge Bomb squared: You aren’t ready for it.

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Theme: The Lord of the Wrings

Author/Opus: *See PDF for details; this is the 546th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Sudoku rules.

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

Solution: PDF and solving animation.

Note: Follow this link for other classic Sudoku. If you are new to this puzzle type, here are our easiest Sudoku to get started on. More Sudoku including variations can be found in these books in our e-store. Also, visit this page to purchase all of the puzzles from the 16th World Sudoku Championship including classic Sudoku.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Twelve Days of Sudoku Discussion post on the GMPuzzles Discord.

Note 3: Please check lesson notes from Dr. Sudoku on Google Docs.

PDF

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

Theme: Variations on a Hungarian Sudoku in Five Minutes

Author/Opus: Unknown; varied by Thomas Snyder, aka Dr. Sudoku, as his 545th puzzle.

Rules: Standard Sudoku rules.

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

Solution: PDF and solving animation.

Note: Follow this link for other classic Sudoku. If you are new to this puzzle type, here are our easiest Sudoku to get started on. More Sudoku including variations can be found in these books in our e-store. Also, visit this page to purchase all of the puzzles from the 16th World Sudoku Championship including classic Sudoku.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our The Twelve Days of Sudoku Discussion post on the GMPuzzles Discord.

Note 3: Please check lesson notes from Dr. Sudoku on Google Docs.