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

Theme: X’s and O’s (Originally for 2014 Arlington Puzzle Festival)

Author/Opus: This is the 208th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Sudoku rules.

Answer String: Enter the 1st row from left to right, followed by a comma, followed by the 9th row from left to right.

Time Standards (highlight to view): Grandmaster = 2:15, Master = 3:45, Expert = 7:30

Solution: PDF

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 classic Sudoku puzzles can be found in The Art of Sudoku, The Art of Sudoku 2 and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

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

Theme: Seeing Double (Originally for 2014 Arlington Puzzle Festival)

Author/Opus: This is the 207th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Sudoku rules.

Answer String: Enter the 5th row from left to right, followed by a comma, followed by the 9th column from top to bottom.

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

Solution: PDF

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 classic Sudoku puzzles can be found in The Art of Sudoku, The Art of Sudoku 2 and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

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

Theme: Jack-O’-Lantern

Author/Opus: This is the 202nd puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Thermo-Sudoku rules.

Answer String: Enter the 3rd row from left to right, followed by a comma, followed by the 4th row from left to right.

Time Standards (highlight to view): Grandmaster = 10:00, Master = 25:00, Expert = 50:00

Solution: PDF; a solution video is available here.

Note: Follow this link for more Thermo-Sudoku puzzles. If you are new to this puzzle type, here are our easiest Thermo-Sudoku to get started on. More Thermo-Sudoku puzzles can be found in The Art of Sudoku 2.

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Theme: One of Each Digit

Author/Opus: This is the 1st puzzle from guest contributor Wei-Hwa Huang.

Rules: Standard Isodoku rules, using numbers 1-8.

Answer String: Enter the 1st “row” from left to right, followed by a comma, followed by the 8th “row” from left to right.

Time Standards (highlight to view): Grandmaster = 8:00, Master = 18:00, Expert = 36:00

Solution: PDF

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

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

Theme: Diamond

Author/Opus: This is the 196th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Sudoku rules.

Answer String: Enter the 4th row from left to right, followed by a comma, followed by the 4th column from top to bottom.

Time Standards (highlight to view): Grandmaster = 5:00, Master = 8:15, Expert = 16:30

Solution: PDF; a solution video is available here.

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 classic Sudoku puzzles can be found in The Art of Sudoku, The Art of Sudoku 2 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: T is for Toplama (Toplama = Addition in Turkish)

Author/Opus: This is the 57th puzzle from our contributing puzzlemaster Serkan Yürekli.

Rules: Standard Sudoku rules. Also, the sum of the digits in each cage must equal the value given in the upper-left corner of the cage. Digits cannot repeat inside a cage.

Answer String: Enter the 5th row from left to right, followed by a comma, followed by the 9th row from left to right.

Time Standards (highlight to view): Grandmaster = 10:00, Master = 16:00, Expert = 32:00

Solution: PDF; a solution video is available here.

Note: Follow this link for more Killer Sudoku and this link for classic Sudoku. More Killer Sudoku puzzles can be found in Killer Sudoku by Serkan Yürekli.

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or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between Sudoku number entry mode and a shading mode to manage the shape inventory.)

Theme: Zero X

Author/Opus: This is the 56th puzzle from our contributing puzzlemaster Serkan Yürekli.

Rules: Standard Shape Sudoku rules.

Answer String: Enter the 2nd column from top to bottom, followed by a comma, followed by the 5th column from top to bottom.

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

Solution: PDF

Note: Follow this link for other less common variations of Sudoku. Many specific variations of Sudoku have their own categories in the sidebar to the left. Follow this link for classic Sudoku.

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Theme: Sudoku GP Round 7 (this puzzle continues a hidden theme present throughout Prasanna’s Sudoku Grand Prix set)

Author/Opus: This is the 41st puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: Standard Sudoku rules. Additionally, all cells having the same digit(s) more than once as orthogonal neighbors are shaded. (If a cell is not shaded, it cannot have any digits repeated as orthogonal neighbors). Or see this example image.

Answer String: Enter the 8th row from left to right, followed by a comma, followed by the 2nd column from top to bottom.

Time Standards (highlight to view): Grandmaster = 9:00, Master = 17:30, Expert = 35:00

Solution: PDF; a solution video is available here.

Note: Follow this link for other less common variations of Sudoku and this link for classic Sudoku. If you are new to this puzzle type, here are our easiest Sudoku to get started on.

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

Theme: Two-Sided Problem

Author/Opus: This is the 187th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Even/Odd Sudoku rules (i.e., cells with a square contain an even digit; cells with a circle contain an odd digit).

Answer String: Enter the 4th row from left to right, followed by a comma, followed by the 2nd column from top to bottom.

Time Standards (highlight to view): Grandmaster = 3:45, Master = 8:00, Expert = 16:00

Solution: PDF

Note: Follow this link for more Even/Odd Sudoku puzzles. If you are new to this puzzle type, here are our easiest Even/Odd Sudoku to get started on. More Even/Odd Sudoku puzzles can be found in The Art of Sudoku 2.

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

Theme: Clue Symmetry and Logic

Author/Opus: This is the 186th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Sudoku rules.

Answer String: Enter the 5th row from left to right, followed by a comma, followed by the 7th column from top to bottom.

Time Standards (highlight to view): Grandmaster = 3:00, Master = 4:15, Expert = 8:30

Solution: PDF

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 classic Sudoku puzzles can be found in The Art of Sudoku, The Art of Sudoku 2 and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.