See more discussion of the puzzles from the United States’ 2021 Puzzle Grand Prix on this post. Note there are some construction details and potential spoilers on that post so view it after you solve.

PDF

or solve online (using our beta test of Penpa-Edit tools using a composite mode where left click inside cell shades square, left click + drag draws line segment, right click inside cell adds dot, and right click on cell edge adds an x.)

Author/Opus: This is the 401st* puzzle from Thomas Snyder, aka Dr. Sudoku (*the 400th puzzle opus number is being held for an upcoming post).

Rules: Standard Yajilin rules: Blacken some white cells and then draw a single closed loop (without intersections or crossings) through all remaining white cells. Blackened cells cannot share an edge with each other. Some cells are outlined and in gray and cannot be part of the loop. Numbered arrows in such cells indicate the total number of blackened cells that exist in that direction in the grid.

Also, in addition to the usual gray clues, some clues are white and black and act similarly to Castle Wall clues. White clues must be inside the loop and black clues must be outside the loop. White and black clues indicate the sum of the lengths of loop segments in the indicated direction.

Difficulty: 2.5 stars (estimate based off competition points; timing standards not available from our usual testers)

Solution: PDF

Note: Follow this link for classic Yajilin and this link for Yajilin variations. Follow this link for more Castle Wall puzzles.

See more discussion of the puzzles from the United States’ 2021 Puzzle Grand Prix on this post. Note there are some construction details and potential spoilers on that post so view it after you solve.

PDF

or solve online (using our beta test of Penpa-Edit tools using a composite mode where left click inside cell shades square, left click + drag draws line segment, right click inside cell adds dot, and right click on cell edge adds an x.)

Author/Opus: This is the 399th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Yajilin rules.

Difficulty: 2 stars (estimate based off competition points; timing standards not available from our usual testers)

Solution: PDF

Note: Follow this link for classic Yajilin and this link for Yajilin variations. If you are new to this puzzle type, here are our easiest Yajilin to get started on. More Yajilin puzzles can be found in The Art of Puzzles 2, in Yajilin by Murat Can Tonta and Prasanna Seshadri, and in our beginner-friendly book Logic Puzzles 101.

See more discussion of the puzzles from the United States’ 2021 Puzzle Grand Prix on this post. Note there are some construction details and potential spoilers on that post so view it after you solve.

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)

Author/Opus: This is the 398th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Castle Wall rules.

Difficulty: 2 stars (estimate based off competition points; timing standards not available from our usual testers)

Solution: PDF

Note: Follow this link for more Castle Wall puzzles. If you are new to this puzzle type, here are our easiest Castle Wall puzzles to get started on. More Castle Wall puzzles can be found in our beginner-friendly collection Intro to GMPuzzles as well as the larger collection Castle Wall, both by Serkan Yürekli.

Earlier in 2021, Thomas Snyder and Serkan Yürekli from Grandmaster Puzzles constructed a Puzzle Grand Prix round. This week we are taking a look back at those puzzles and will be adding some extra notes on the constructions here.

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Our past week of Sudoku puzzles is collected in this PDF and the solutions are in this PDF.

The daily solution videos are on the posts and linked below:

We’ve recently added Penpa solving modes for all of our Pentominous and Fillomino puzzles dating back to 2013. Throughout the year we’ve gotten 1350 puzzles digitized (completed genres listed here) and had over 200,000 clicks into our Penpa puzzles. We’re hoping to keep growing that number into 2022 (500k+) and expect to have everything digitized in the next few months. There are some other recent Penpa improvements we’ll be rolling out in the next week and telling you more about. We’ll also be spending some time looking back at our Puzzle Grand Prix puzzles from Serkan and me, and then announcing our Best of 2021 web puzzles, reflecting on our 2021 objectives and key results and sharing our 2022 plan.

PDF

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

Theme: Christmas Tree

Author/Opus: This is the 397th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Thermo-Sudoku rules.

Difficulty: 4.5 stars

Time Standards (highlight to view): Grandmaster = 7:30, Master = 16:30, Expert = 33:00

Solution: PDF; a solution video is also 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 and Masterpiece Sudoku Mix 2.

Our past week of Pentomino puzzles is collected in this PDF and the solutions are in this PDF.

The daily solution videos are on the posts and linked below:

Our last week of puzzles for 2021 will feature Sudoku and variations.

Our past week of Nanro puzzles is collected in this PDF and the solutions are in this PDF. Also, we just finished digitizing all of our Nanro puzzles for Penpa-Edit solving so check out our archive.

The daily solution videos are on the posts and linked below:

We’re reaching the end of 2021 with two more weeks of puzzles. This next week features six different puzzles involving Pentominoes.

PDF

or solve online (using our beta test of Penpa-Edit tools; use the tab key to alternate between shading and number entry modes)

Theme: Centered Squares

Author/Opus: This is the 396th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Nanro rules.

Difficulty: 2 stars

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

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

Note: Follow this link for Nanro puzzles on this website and this link for variations on Nanro puzzles. If you are new to this puzzle type, here are our easiest Nanro Puzzles to get started on. More Nanro puzzles can be found in A Number o’ Nanro by Prasanna Seshadri.

There are two more days left in our e-store sale. Any purchase of $25 or more will get a 20% discount automatically taken off at our web store. The discount applies to all of our books, including our two latest, Arrow Sudoku and Outside Sudoku, from the Masterpiece Sudoku Mix series.

Our past week of “Two puzzles, one grid” is collected in this PDF and the solutions are in this PDF.

The daily solution videos are on the posts and linked below:

and there will be a Sunday Stumper (also with a second valid puzzle style like the rest of this past week) posting soon.

This next week will feature Nanro puzzles.