Here is a (very hard) sample puzzle from the Killer Sudoku puzzle pack by Serkan Yürekli, which was just added to our e-store.

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

Theme: Time Killer

Author/Opus: This puzzle comes from our managing editor Serkan Yürekli as part of his new e-book.

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

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 11:00, Master = 24:00, Expert = 48:00

Solution: PDF; a solution video from Cracking the Cryptic will be 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)

Theme: Sum Central

Author/Opus: This is the 192nd puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: Standard Kakuro Rules.

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 8:00, Master = 10:45, Expert = 21:30

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

Note: Follow this link for classic Kakuro and this link for Kakuro variations. More Kakuro puzzles can be found in Kakuro and Variations by Serkan Yürekli and in The Art of Puzzles 2.

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

Theme: Kakuro Time

Author/Opus: This is the 4th puzzle from guest contributor Salih Alan.

Rules: Standard Kakuro Rules.

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 4:15, Master = 6:45, Expert = 13:30

Solution: PDF

Note: Follow this link for classic Kakuro and this link for Kakuro variations. More Kakuro puzzles can be found in Kakuro and Variations by Serkan Yürekli and in The Art of Puzzles 2.

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

Theme: Clueless

Author/Opus: This is the 366th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Thermo-Sudoku rules.

Difficulty: 4 stars

Time Standards (highlight to view): Grandmaster = 6:15, Master = 10:00, Expert = 20:00

Solution: PDF; a solution video from the author is also available here and another from Cracking the Cryptic is 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 and Masterpiece Sudoku Mix 2.

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

Theme: Vacant Room

Author/Opus: This is the 5th puzzle from guest contributor Akash Doulani.

Rules: Standard Arrow Sudoku rules.

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 5:30, Master = 7:30, Expert = 15:00

Solution: PDF

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)

Theme: XV

Author/Opus: This is the 56th puzzle from our contributing puzzlemaster Ashish Kumar.

Rules: Standard Sudoku rules. Also, whenever the numbers in two adjacent cells sum to exactly 10 or 5, an X or V is placed on the edge between cells reflecting the Roman numerals for 10 or 5. All adjacent cells not marked with an X or V cannot add up to 10 or 5.

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 4:00, Master = 7:00, Expert = 14:00

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

Note: Follow this link for other 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.

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: Uncommon Patterns

Author/Opus: This is the 45th puzzle from our contributing puzzlemaster Tom Collyer.

Rules: Standard Slitherlink rules.

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 4:30, Master = 7:30, Expert = 15:00

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

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.

PDF

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

Theme: Initial Impressions

Author/Opus: This is the 331st puzzle from our contributing puzzlemaster Grant Fikes.

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

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 4:45, Master = 7:30, Expert = 15:00

Solution: PDF; a solution video is also 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.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode, shape (star) placing mode, and the linex mode where left click+drag draws lines and right click marks X’s)

Theme: White Hole

Author/Opus: This is the 306th puzzle from our managing editor Serkan Yürekli.

Rules: Standard Balance Loop rules. Also, each row and column must contain exactly two stars. Stars cannot be placed in adjacent cells that share an edge or corner, and all stars must be on empty cells not used by the loop.

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 13:00, Master = 18:30, Expert = 37:00

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

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 in linex mode where left click+drag draws lines and right click marks X’s)

Theme: Pairs

Author/Opus: This is the 184th puzzle from our contributing puzzlemaster Murat Can Tonta.

Rules: Standard Balance Loop rules. Also, numbers outside the grid show the number of separate loop segments visible in that direction. A segment of length N in a given direction is taken as a building of height N. Buildings of height N block the view of all buildings behind them of equal or lesser height.

Also, see this example:

Difficulty: 3.5 stars

Time Standards (highlight to view): Grandmaster = 4:30, Master = 7:00, Expert = 14:00

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

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.