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 numbers in each cage must equal the value given in the upper-left corner of that cage. Numbers 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)

Author/Opus: This is the 332nd puzzle from our contributing puzzlemaster Grant Fikes.

Rules: Variation of Kakuro. Some 2×2 white regions are to be shaded gray and treated as single (2×2) cells in the Double Kakuro, the position of these cells must be found while solving, and each gray cell is to be filled by a single digit which sits in multiple rows and columns. No digits can repeat within an entry, regardless of whether they are in small or large cells.
(An example Double Kakuro puzzle is linked.)

Difficulty: 2.5 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 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.

PDF

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

Theme: Crossword

Author/Opus: This is the 70th puzzle from our contributing puzzlemaster John Bulten.

Rules: Standard Kakuro Rules.

Difficulty: 2.5 stars

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

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.

PDF

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

Theme: Five Rooms

Author/Opus: This is the 367th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Kakuro Rules.

Difficulty: 2 stars

Time Standards (highlight to view): Grandmaster = 1:20, Master = 1:45, Expert = 3:30

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.

PDF

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

Theme: Cross Sums

Author/Opus: This is the 308th puzzle from our managing editor Serkan Yürekli.

Rules: Standard Kakuro Rules.

Difficulty: 1 star

Time Standards (highlight to view): Grandmaster = 0:45, Master = 1:20, Expert = 2:40

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.

PDF

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.