This year, we are going to have some extra difficult Sunday Stumpers, about once a month. These will be quite tough puzzles, but with a logical path to be found (and solution videos to help). This first Sunday Stumper is a challenging Sudoku variation in the style of some of the unusual rule mash-ups and difficulty seen on the Cracking the Cryptic channel.

PDF

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

Theme: Have a Cracking New Year!

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

Rules: Standard Sudoku rules. Some arrow shapes are in the grid; the sum of the digits along the path of each arrow must equal the digit in the circled cell (digits can repeat on an arrow). Some thermometer shapes are in the grid; the digits along the thermometer must be strictly increasing from the round bulb to the flat end. Some rectangular cages are in the grid marked by dashed lines; the sum or product of the digits in these cages must be either 20 or 21. Finally, some arrows are given outside the grid; the sum or product of the digits along these marked diagonals must be either 20 or 21 (digits can repeat on a diagonal).

Difficulty: 5 stars

Time Standards (highlight to view): Grandmaster = 15:00, Master = 30:00, Expert = 60:00

Solution: PDF; a solution video from Cracking the Cryptic is here.

Note: Follow this link for other variations on Sudoku.

PDF

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

Theme: 2021

Author/Opus: This is the 370th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard TomTom rules, using the integers 1-7.

Difficulty: 2.5 stars

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

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

Note: Follow this link for classic TomTom and this link for TomTom variations. If you are new to this puzzle type, here are our easiest TomTom to get started on. More TomTom puzzles can be found in the TomTom collection, in The Art of Puzzles, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

Dear solvers,

I hope you all enjoyed the “Best of 2020”. The collected PDFs are in all the web posts and also on our all weekly PDFs page.

Our “Best of …” selection process tried to be as consistent as possible with prior years, but some technical issues with the solving/fave widget meant we did add in web comments and tester feedback as additional signal for the best puzzles. If you think we missed a particularly awesome puzzle, please tell us (and in 2021 keep commenting on the posts when you like something as that is the most direct way for authors to see your feedback).

One small update on the solving widget: there are still users with login issues and the necessary fix requires a larger lift-over of the tool and database to our servers; we’ve contracted for this project so hope it returns to its old form in the next couple months.

One big update for 2021 is that we are going to include a digital solving option with automated solution checking for all puzzles.* We have set up Penpa-Edit on our site, and will be using it in a kind of “beta” mode as we find the best ways to present a variety of puzzles (with good documentation/instructions) including making some style changes over the coming months to integrate the current version more with the site. At the start, a lot of the help may be missing so if you aren’t already an experienced Penpa user, please look for some of our first solving videos to help a bit.

One last update for now is that in 2021 we will have a few “Sunday Stumpers” that are very, very hard puzzles. Seeing how difficult puzzles can seem fair to post if there are solving walkthroughs eventually connected to show the logical route, we will try to post a Sunday Stumper once a month including next Sunday at the end of our “Welcome to 2021” week. New puzzles, including the first with penpa-edit, will start tomorrow.

Best wishes for a great 2021,
Thomas (aka. Dr. Sudoku)

(*One impressive thing about Penpa-Edit as it has grown is that we can cover 99+% of the puzzles we’ve posted in the past — there is only one puzzle in our initial weeks of 2021 where a slight modification will be required to present the puzzle in a solvable form.)

Here are our best Sudoku puzzles of 2020, in chronological order, selected from the 32 web posts in this category based on FAVE votes, web comments, and tester comments. All of these puzzles are gathered in this PDF file.

With 1 day left before our official reopen, Dr. Sudoku shared this minimal clue “countdown” Consecutive Pairs Sudoku puzzle that got a good number of FAVE votes.

A few months later, guest contributor Bryce Herdt’s Thermo-Sudoku ran “hot” with our solvers, with a nice visual theme and fun solving path to the answer.

While on the easier side, this “Big X” Consecutive Pairs Sudoku from Thomas Snyder was another favorite sudoku puzzle from the year.

A few classic sudoku got strong reviews through the year, but none more so than this excellent Sudoku by Swaroop Guggilam which was clearly one of our Best 2020 Sudoku.

Our final best of 2020 Sudoku comes from Ashish Kumar who made an XV Sudoku with a theme referring to the letters, and a pretty minimal path taking advantage of the “XV rules” throughout.

Here are our best Object Placement puzzles of 2020, in chronological order, selected from the 33 web posts in this category based on FAVE votes, web comments, and tester comments. All of these puzzles are gathered in this PDF file.

This Star Battle puzzle from Thomas Snyder (our first in many months that announced we were coming back) got the most FAVE votes for the year, but probably as much for the news as for the puzzle itself, with 22 stars to be placed with 22 days before re-launch.

Serkan Yürekli wrote this favorite Battleships with a slightly unusual solving path that solvers enjoyed.

Guest contributor JinHoo Ahn wrote another of our Best of 2020 puzzles with this “Double Numbers” Battleships with a very elegant theme and solving path.

2020 featured a lot of Star Battle puzzles on the site and in our store; this Star Battle from Ashish Kumar with a nice symmetric set of regions got a good response from our solvers.

Our final best of 2020 in object placement came in October from Murat Can Tonta, with a Statue Park themed around the corner placements.

Here are our best Number Placement puzzles of 2020, in chronological order, selected from the 32 web posts in this category based on FAVE votes, web comments, and tester comments. All of these puzzles are gathered in this PDF file.

Our reopening announcement puzzles got a lot of attention and Thomas Snyder’s TomTom puzzle with two spirals counting down 15 days to go was a favorite Number Placement puzzle of 2020.

John Bulten constructed another great TomTom variation, TomTom (Cipher), where solvers appreciated the different logical steps to get to the one solution.

Blending the “thermometer” constraint with standard Skyscraper rules led to this clueless Thermo-Skyscrapers puzzle from Serkan Yürekli that got favorable feedback.

Another Skyscrapers puzzle that was well liked was this challenging 6×6 puzzle by Ashish Kumar with a fairly narrow logical path.

Our final Best of 2020 in Number Placement came from Prasanna Seshadri: this
Kakuro puzzle with a fun (but hard) solving path.

Here are our best Shading puzzles of 2020, in chronological order, selected from the 32 web posts in this category based on FAVE votes, web comments, and tester comments. All of these puzzles are gathered in this PDF file.

A few of our best Shading puzzles were “Skyscrapers” variations with outside clues driving the solve. The first of these comes from guest contributor Freddie Hand: Tapa (Skyscrapers).

More shading + skyscrapers came soon thereafter from Prasanna Seshadri with this great Kurotto (Skyscrapers) puzzle.

Many April Fool’s Days ago I made an audiobook TomTom set of puzzles (that was not just a set of fools) which was followed a few years later by a Cross the Streams (audiobook) by Grant Fikes. Grant revisited this clever idea in 2020 with a new Cross the Streams (audiobook) that was a favorite shading puzzle.

December brought two great LITS puzzles, starting with this LITS by JinHoo Ahn with an elegant theme (and quite approachable difficulty).

Our last best shading puzzle of 2020 is this more challenging LITS by wormsofcan that asked solvers to think outside the box.

Here are our best Region Division puzzles of 2020, in chronological order, selected from the 31 web posts in this category based on FAVE votes, web comments, and tester comments. All of these puzzles are gathered in this PDF file.

The Saturday challenge from our first week of web puzzles was a delightful Fillomino puzzle from guest contributor Elyot Grant.

As we reached the end of June, we posted what was one of the highest rated (and also fairly hard) puzzles of the whole year: a Pentominous by JinHoo Ahn, another guest contributor who surprised us with a lot of great submissions this year.

Puzzlemaster Prasanna Seshadri shared an Araf puzzle with different clusters of small and big numbers and a very elegant logical solving path.

November included a really great Cave puzzle from William Hu, with a beautiful all odd theme and clever logic to be found on the solving path.

And our last post of 2020 also got a good response from our solvers and closes out this Best of set: this Fillomino (Checkered) variation by Jonas Gleim.

Here are our best Loop/Path puzzles of 2020, in chronological order, selected from the 26 web posts in this category based on FAVE votes, web comments, and tester comments. All of these puzzles are gathered in this PDF file.

A lot of our early puzzles as we were relaunching the website got a good number of FAVE votes. And we seemed to start out strong with this first regular post: an antisymmetric no-numbers Balance Loop by Murat Can Tonta.

Murat had another favorite puzzle with this “Parallel Universes” Slitherlink with an interesting logical path around the grid.

Serkan Yürekli put a little uncertainty into this Slitherlink variation with several missing numbers that must fulfill Sudoku-like constraints. The logical challenge got a lot of favorable comments.

Serkan delighted us again in September with a visually beautiful Snake (Cipher) puzzle that announces itself on the outside of the grid.

Our final best Loop/Path puzzle of 2020 comes from this November post from Tom Collyer, who focused on some less common patterns to give us a really challenging Slitherlink.

This was our last week of puzzles for 2020. You can find the set of Fillomino puzzles in this PDF and the solutions are all grouped in this PDF and have also been linked to the individual posts.

We have a solving video for the last two puzzles in the week, including Friday’s Catch-13 Fillomino by Ashish Kumar:

and Saturday’s Fillomino (Checkered) by Jonas Gleim:

We also have a holiday gift for everyone, as we have posted all of our solving videos from before 2020 on Youtube (a total of over 100 walkthroughs)! These are linked to the individual posts if exploring the old archive and also captured on this page. These were filmed with earlier techniques, so some have slightly worse visual/audio quality than we are trying to achieve now, but there is a lot to learn by exploring the videos. I will soon have a new document camera to improve my recording even more, and next year may even try some new kinds of videos like blind solves of competition puzzles and also “basic rules and info” videos for the puzzle styles to better introduce beginners to a new style including its history and basic constraints. Tell us what you’d like to see from future solving videos.

We’ll be taking the next two weeks off to organize our Best of 2020 list and prepare for the start of 2021 puzzles. 2020 has been a full (if challenging) year, with me starting a new job in March and having a lot more responsibilities in leading a large team advancing immunology assays as potential diagnostic tests across diseases. But by adding Serkan Yürekli as our Managing Editor, we together got back to posting 30 straight weeks of puzzles, with at least 2 solving videos each week, and also released 7 new books of puzzles. We have a lot to come in 2021, including more books, the implementation of more routine online solving, a new puzzlemaster and more.