### WSC Playoff Puzzle 8/10: Isodoku by Thomas Snyder

The eighth playoff puzzle for the World Sudoku Championship playoffs, reflecting the unusual grids of the “Grid-Breaking” round, is this Isodoku by Thomas Snyder.

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

Author/Opus: This is the 456th puzzle from Thomas Snyder, aka Dr. Sudoku.

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

Estimated Difficulty: 2.5 stars

Solution: PDF for all playoff puzzles.

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

### Isodoku by Serkan Yürekli

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Theme: Step Pyramids

Author/Opus: This is the 347th puzzle from our managing editor Serkan Yürekli.

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

Difficulty: 2 stars

Time Standards (highlight to view): Grandmaster = 1:15, Master = 2:15, Expert = 4:30

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

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

### Isodoku by Serkan Yürekli

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

Theme: Pamukkale Travertines

Author/Opus: This is the 325th puzzle from our managing editor Serkan Yürekli.

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

Difficulty: 3.5 stars

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

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

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

### Isodoku by Thomas Snyder

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

Theme: Don’t Worry

Author/Opus: This is the 371st puzzle from Thomas Snyder, aka Dr. Sudoku.

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

Difficulty: 2 stars

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

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.

PDF

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

Theme: Clue Symmetry and Logic

Author/Opus: This is the 128th puzzle from our contributing puzzlemaster Prasanna Seshadri.

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

Answer String: Enter the 5th “row” from left to right, followed by a comma, followed by the 7th “row” from left to right.

Time Standards (highlight to view): Grandmaster = 4:00, Master = 6:00, Expert = 12:00

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.

PDF

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

Theme: Clue Symmetry and Logic

Author/Opus: This is the 127th puzzle from our contributing puzzlemaster Prasanna Seshadri.

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

Answer String: Enter the 5th “row” from left to right, followed by a comma, followed by the 7th “row” from left to right.

Time Standards (highlight to view): Grandmaster = 2:30, Master = 4:00, Expert = 8:00

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.

### Isodoku by Serkan Yürekli

PDF

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

Theme: Symmetry and Logic

Author/Opus: This is the 98th puzzle from our contributing puzzlemaster Serkan Yürekli.

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

Answer String: Enter the 5th “row” from left to right, followed by a comma, followed by the 7th “row” from left to right.

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

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.

### Isodoku by Wei-Hwa Huang

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

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.

### Isodoku by Thomas Snyder

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

Theme: Heart-Shaped Box

Author/Opus: This is the 160th puzzle from Thomas Snyder aka Dr. Sudoku.

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

Answer String: Enter the 5th “row” from left to right, followed by a comma, followed by the 8th “row” from left to right.

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

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.

### Championship Chatter – Somewhat Irregular

Two more from the US Sudoku Qualifying Test in May — both geometric departures from regular sudoku.

As I consider the 2012 Irregular on the USSQT one of my best puzzles from that year, it was obviously going to be a challenge to do as well this time around. I felt the puzzle below was an adequate follow-up but certainly not as good as last year’s. The solve is meant to take advantage of the slightly irregular spacing of 1-6 in the patterned middle with the extra 7’s and 8’s giving a single solution. Note there are no 9s anywhere in the grid. Some Law of Leftovers steps will likely be encountered before the finish.

For the isodoku, just before the US Qualifier test, one of our readers here suggested I make a tutorial on some of the forced rules that come with these 3d shapes (this was after an isometric TomTom that strongly required solvers to know only 2 of each digit could appear on each face). I obviously couldn’t post such a tutorial just before the USSQT, but the properties of the 3D shapes was strongly in mind here. Often — like in the standard 2×4 rectangle form of an isodoku, or the 2012 USSQT Isodoku — there is a strong 2×2 square requirement that can split the digits into two distinct sets throughout the puzzle (see this colored solution of the 2012 for example). This year I wanted to choose a geometry that almost seems like it needs that 2×2 requirement in places, but here only three digits are highly constrained and the attempt to split the shape into patterns falls apart. Can you spot the three constrained digits and sort out where they must always go in this kind of geometry? Six particular cells are key.

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

Theme: Pattern in regions and digits

Rules: Standard Sudoku rules. The regions are not 3×3 boxes but are instead irregular shapes indicated by the bold lines.

Answer String: For the USSQT, the answer strings were a set of rows/columns encountered late in the puzzle. For this week, you can just hit the solved button on an honor system if you think you’ve solved it.

Solution: PDF

PDF

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

Theme: Stacked boxes

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

Answer String: For the USSQT, the answer strings were a set of rows/columns encountered late in the puzzle. For this week, you can just hit the solved button on an honor system if you think you’ve solved it.

Solution: PDF