Archive for the ‘Competition Discussion’ Category:

2021 Puzzle Grand Prix: US Round Retrospective

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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Ask Dr. Sudoku #17: Thoughts on digital solving options and puzz.link

[Update: As of 2021, we are now routinely using penpa-edit and more info is here.]

While I am mainly a pencil-and-paper puzzle solver, I always thought GMPuzzles would eventually find some digital outlets. Not necessarily one outlet — our different styles have different needs and a good app for Sudoku/TomTom is probably quite different from a good app for Tapa/Nurikabe — but at least some outlets where we would be content providers. While I will soon have some of my TomTom puzzles as part of one app-based release, this is the exception and not the rule after 7.5 years.

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Ask Dr. Sudoku #16 – V for Victory?

Q: Are you going to write about your experiences in Prague this year? Did you expect you would ever win the World Puzzle Championship?

Several people have asked if I would write a report on my experiences this year as I finally became World Puzzle Champion. Long ago, before I started this site, I would frequently write live blogs during or shortly after puzzle events, capturing the “heat” of competition. Some wanted to see me write an epilogue, after so many close runner-ups, to conclude a chapter in my life. Many of these championship stories (when posted in the late aughts) were the first ways people learned about me. I now prefer to let my own volume of written and edited puzzles speak more for me.

The live blogs capture my moments of great success and also great failure, as someone writing with full transparency and passion about what it is like to compete. I shared photos of “dirty laundry” — the stupid mistakes a competitor can make. I gave complaints earned and unearned against event organizers (the “So yeah, [insert event] happened” posts). I wrote an open letter that led to disqualifying a cheater and another that unfortunately did not lead to any WSC competition changes and continuing questions about what a Sudoku is almost 10 years later, ….

I stopped posting on that blog in 2013, with a primary focus on my own scientific career and a secondary focus on growing GMPuzzles. The reconnecting with science jobs was a major reason I stopped going to competitions from 2014 until 2017, “retired” from competitive puzzling in a sense. I never fully explained that choice, and I’ve never explained a few things that have had the most impact on my adult life. I’ve separated my very public “puzzle life” from my private life.

This time it is hard for me to answer questions like “did you expect you could win this year?” or “how does it feel?” without starting from a more private angle.

For the very private and introspective angle, continue here (note: some sadness/personal loss covered).

To go straight to the competition report, click here.

The Playoff story and video annotation is here.

US Puzzle Championship Thread

We’ll have a little more discussion in the comments here later after the dust settles about the puzzles, but we hope everyone enjoyed today’s US Puzzle Championship.

Our puzzlemasters contributed several puzzles to the competition including:

Crosslink by Grant Fikes
Double Minesweeper by Serkan Yürekli
Nurikabe Path by Thomas Snyder
Star Search by Thomas Snyder
Tapa by Serkan Yürekli
Tapa View by Prasanna Seshadri
Wind Shield by Serkan Yürekli
Wordmark by Serkan Yürekli

Championship Chatter – Final Puzzles and Thoughts

Here are the final puzzles from the US Sudoku Qualifying Test that I wrote. Both are less common types. Tomorrow will finally bring some new puzzles, and I hope some surprises too.

The first of this set, a “Seek-and-Spell” variant, is a style that took on a life of its own on this website a few months ago as more and more constructors kept submitting it. I wanted a very United States sort of puzzle somewhere on this test and found a good letter set to get 5 states into this grid. I wanted OHIO from the start as an easy Seek-and-Spell rule placement. But the value of states like MONTANA and INDIANA became clear during construction. This may have been the only case on the test where some non-sudoku logic puzzling skill would really accelerate the solve as the Seek-and-Spell placements are quite limited and getting them fixed makes the rest much easier.

The second of this set is a style I first created for a Czech/US Sudoku Championship several years ago and one that I keep bringing out every year typically for championship season. It is one of the easier styles construction-wise to get started with creative themes as it does not take a lot of digits in either grid before the linked cells really start to force the solve. But occasionally getting both grids to behave by the end can be hard. Here, my seeds were two different styles of basic step in the two grids. And after finding the linked regions, consistently ping-ponging between the two puzzles to get to the end. It is another of my favorites on this test.

Not posted this week were the great submissions from Wei-Hwa Huang. This year I gave him a sketch of the styles I wanted and he delivered in a large way. For example, I had a basic concept to play with Binary in a 6×6 grid with missing digits much like the Indian GP test had a play on this with Braille. Wei-Hwa took it farther than I did though with 0-7 and three bits being a perfect choice and his example and test puzzle were both quite fun. The Property Sudoku also had quite an elegant solve and his Diagonal had a good, but fair, challenge.

Sudoku by Thomas Snyder

PDF

Theme: United States

Rules: Standard Sudoku rules except that instead of the numbers 1-9 this puzzle uses the letters ADEHIMNOT. Also, clues in the grid represent typical “Seek and Spell/Kanaore” clues; specifically, it must be possible to read each of the words/phrases listed below the grid by starting at the indicated number, moving one cell in the direction indicated by the arrow, and then continuing to move one cell at a time up, down, left, or right to complete the word/phrase. No cell may be used more than once in a single path, but the same cell can appear in the paths of different words/phrases.

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.

Sudoku by Thomas Snyder

PDF

Theme: Logical

Rules: Standard Sudoku rules for each of the two grids. There are three shaded regions in each grid. The shaded regions must exactly match between the puzzles, but which shaded regions correspond to which must be discovered.

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.

Championship Chatter – Which Came First: the Arrow or the Thermo?

This puzzle was inspired by a comment I read somewhere of someone stumbling on a Thermo-Sudoku by solving it for awhile as an Arrow (or vice-versa, I can’t remember exactly). The goal was simple: can I make one puzzle that solves both ways depending on the type of shape placed into the grid. The theme here speaks mostly for itself.

But if you want an extra challenge I’d recommend solving from these images (Arrow / Thermo) or PDFs (Arrow / Thermo) which contain the original draft of the finished puzzle. The arrow is probably a much better challenge as a result, but the Thermo is at the very high end of the difficulty scale and better for a slow solve than a competition solve. Fortunately there were a good set of symmetric positions that still matched with digits so I could add clues to both puzzles without spoiling the theme. Of course, almost all the remaining digits differ but I guess that is the point.

Some people have asked about the construction steps to get two working puzzles of very different types. I normally design both of these styles by hand starting from an image of the shapes and then slowly adding digits. Here I simply did this at the same time for two different styles. The intention of having the centers work quite differently in the two types made the first four givens in the center the start. The 1’s in the corners were also great clue digits for both Arrow and Thermo types for different reasons. As I got some other good logical placements worked out, I did use some software tools to confirm each puzzle still had possible solutions before going too far down a dead-end. Gradually a duplicated puzzle came into form.

Enjoy what were probably my favorite puzzles from the USSQT.

Arrow Sudoku by Thomas Snyder

PDF

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

Theme: Deja vu

Rules: Standard Arrow Sudoku rules.

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

Thermo Sudoku by Thomas Snyder

PDF

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

Theme: Deja vu

Rules: Standard Thermo-Sudoku rules.

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

Championship Chatter – The Sudoku Dynasty Begins

Two more from the US Sudoku Qualifying Test in May.

The first, a Tile Sudoku, is a pattern I’ve used before but not in my recent GMPuzzles series of Tile Sudoku. Like almost every single one of these Tile Sudoku, there are “meta-constraints” forced by the geometry change that make the solve easier. First, all the 2×2 squares form a 1-9 set, which is not that hard to prove. But did you notice that each 1×3 rectangle made out of a 1×2 + 1×1 cell is part of a triplet of such rectangles that will contain the digits XY, YZ, and ZX? Because each of these 12 groups of linked 1×3 rectangles need at least one given placed into them, this 16 given puzzle is pretty close to minimal for the geometry. This puzzle’s goal was to have a clean 1-8 clock in one of the two symmetric groups, and then a choice of the remaining digits to leave a non-trivial solve even if solvers know about some of the hidden groups.

The second puzzle – Dynasty Sudoku – was a newer style for me. It’s an idea I’ve had in the back of my head to use a lot in a kind of follow-up to Mutant Sudoku. But I had not put it to paper before Adam R. Wood debuted it on the 2011 USPC. Of course his grid needed irregular regions and a 12×12 size to get a lot out of the dynasty rule. I challenged myself to make an interesting 9×9 puzzle with regular regions that still required several deductions based on not closing off the white spaces and I think I succeeded with this puzzle.

Sudoku by Thomas Snyder

PDF

Theme: Pattern in regions and digits

Rules: Standard Tile Sudoku rules.

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.

Sudoku by Thomas Snyder

PDF

Theme: Logical

Rules: Variation of Sudoku rules. Place the digits 1 through 7 and two black cells in each row, column, and 3×3 region. Additionally, the black cells do not touch each other on the edges, and the white cells must form a single connected region.

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.