Archive for the ‘Contests’ Category:

Contest Update: Linking 200 Cells

We have now added the solution to the Linking 200 Cells puzzle to the website (and if anyone was looking for “hints” as opposed to solutions, we will now be able to add those into the comments on the website). There were 33 correct submissions out of about 40 entries. The three randomly selected winners, who have each won an e-book from Prasanna Seshadri, are Yossi Fendel, Tom Luo, and Arthur Nebout. Congratulations to these three, and we hope you all enjoyed the puzzle!

Contest Puzzle: Linking 200 Cells by Prasanna Seshadri

Prasanna is celebrating two milestones this week and we will have two special large puzzles. The first one here recognizes Prasanna’s 200th submission on GMPuzzles, and combines three of the styles where Prasanna has written books for our e-store.

Puzzle by Prasanna Seshadri

(view directly for a larger image)


or solve online (using our beta test of Penpa-Edit tools; while solution checking is not enabled, if you are comfortable with the different tool selection options you should be able to fully solve the puzzle in this mode too.)

Theme: Linking 200 cells

Author/Opus: This is the 200th puzzle from our contributing puzzlemaster Prasanna Seshadri.


Grids 1-2: Follow regular LITS rules. Between the two LITS grids, the corresponding white cells can never both be shaded, while the corresponding gray cells must be identical in the three 200-shaped regions.

Use the LITS solutions and your ingenuity to discover the needed constraints for Grids 3-4. For Grid 3, you will find that some gray circles must change color to white or black.

Grid 3: Follow regular Balance Loop rules. Additionally, the loop must cross itself if it passes through a gray circle. The loop must go straight throught the gray circle both times; in one direction the path behaves as if the circle is white with equal loop lengths, and in the other direction the path behaves as if the circle is black with unequal loop lengths. It is not required that the loop pass through all of the gray circles (but it must pass through all white and black circles). (See also the image below.)

Grid 4: Follow regular Yajilin rules.

When taken together, the grids yield a short final answer! Send this (less than five character) string to hiddencontest at gmpuzzles dot com by March 14th, 2021 to be eligible to win an e-book by Prasanna Seshadri. The contest is now closed and results summarized here.

Difficulty: 5 stars?

Solution: PDF

Contest Update

(I still have a massive backlog of things to do since my move because I’m really dedicating most of my time and energy to my new position with Google Life Sciences. So for those looking for more site updates, you’ll still need to wait. For now I can finally write up a report on our Hidden Contest from late March.)

John Bulten’s debut week was quite ambitious and challenging even before considering the equally ambitious and challenging hidden contest that ran through the entire week. Every contributing grandmaster is given complete freedom to design a debut week of puzzles. Despite this freedom, a certain theme has come up each time. This inspired John’s hidden contest. Read on to see what was going on:

Contest and Schedule for Next Week

We hope you enjoyed all John’s puzzles from last week, which are fully contained in this PDF. If you solved the complete set, Grandmaster Puzzles would like to reward you with a copy of the seminal reference “A Dictionary of 4,573 Crucial Cross Words and their Clues”, coauthored by John Bulten. This out-of-print 1987 work was the first crossword dictionary we know of to rank words using the methodology now standard for “The New York Times”. All copies will be personally signed by J.B.!

To obtain your copy, simply enter the proper product code (read: the answer to the hidden puzzle) in the applet below before midnight, April 19th (three weeks from today) May 3rd May 17th, so that we can verify your address via email. Solvers will also be recognized in a later post.

As with our first Hidden Contest, this is a challenge of logic and observation. We’ll be adding hints here each week until the close of the entry period.

Hint 1 (4/5/2015): It’s all good, but I recommend 138956247.

Hint 2 (4/12/2015): To obtain the product code, simply follow the correct instructions in the correct order. A review of other puzzlemaster debut weeks may help out.

Hint 3 (4/19/2015): Following the example of other puzzlemasters here, John tried to leave his mark on these puzzles. After finding out what that means, you are looking for an answer with one word followed by several numbers.

(4/26/2015): No extra hint today, but we’re sharing the official solution packet for the week’s puzzles which may be useful.

Hint 4 (5/3/2015): You are looking for a single element in common across all of the puzzles. It may be easiest to find this by looking at the solutions that include shading (BACA, Slithersweeper, and Tapa).

Next week will be a regular variety mix with puzzles from six authors.

Schedule for Next Week

All the puzzles from last week’s Castle Wall collection can be found in this PDF.

We had 57 solvers for Dr. Sudoku’s 200th puzzle contest. Two random numbers were selected from 1-57 using marking solvers 30 and 52 as the winners of a free puzzle book. Those lucky solvers are (30.) Projectyl and (52.) phlebowitsh.

For anyone who was stumped by the lack of rules for the TomTomTom, and didn’t catch on to the hint provided by the title, here are complete rules. The six 6×6 grids make up a Latin Cube where no digit repeats in any row or column within a grid, or within any cell in the same position across the grids (i.e., stack the grids on top of each other and no digit repeats within a position in that stack). While none of the starting grids have a unique solution without the Latin Cube constraint, with this constraint all five regular looking TomToms can now be uniquely solved. Use the remaining digits in each location to fill in the last grid. Assign number values to those cases keeping in mind operations when present and convert 1=A, 2=B, …, to read out the solution in left-to-right, top-to-bottom order.”

This next week will feature both letters and numbers. Specifically, a set of Pentominous puzzles by Grant Fikes and Sudoku puzzles by Thomas Snyder. The bonus puzzle for our high-level supporters will also be a Pentominous by Grant Fikes.

TomTomTom by Thomas Snyder

Note: This puzzle is a contest puzzle. All correctly submitted answers (in the applet below the puzzle) before November 9th will be entered into the contest drawing. Two solvers will each get a Grandmaster Puzzles/Thomas Snyder puzzle book of their choice.

TomTomTom by Thomas Snyder

(view directly for a larger image)


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

Theme: 200th Puzzle Contest Spectacular

Author/Opus: This is the 200th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: To be determined by solver. (Edit: the full rules are now available on this post.)

Answer String: Enter the final answer as a single string of twelve capital letters.

Time Standards (highlight to view): Grandmaster = 20:00, Master = 35:00, Expert = 1:10:00

Solution: PDF

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

Contest Update

On May 26th, in recognition of our Contributing Puzzlemaster Grant Fikes’ birthday, a Sunday Surprise contest was posted. 29 solvers have completed the puzzle and all were added to a drawing Grant describes here.

The winner of the random drawing is FoxFireX, who will receive a copy of Battle of LITS.

Sunday Surprise #5 – Seeing Stars (and a contest)

Today’s surprise marks the occasion of Grant Fikes’ 26th birthday. Grant has written a surprise puzzle hunt-style puzzle that will solve to a two word answer. This is likely more challenging than our earlier “Word Search” surprise on April 1st, but we hope it is enjoyable to those who give it a shot while celebrating Grant’s birthday.

Note: the first 26 solvers (or all those who solve it within a week if fewer than 26 solve it by then) will be entered into a random drawing for a copy of Grant’s “Battle of LITS” board game.

Surprise Puzzle by Grant Fikes


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

Answer String: Enter the two word answer in all capital letters, with a single space between words.

Solution: PDF

Update (6/2/13): There have been 27 solvers in the week since this puzzle posted and all of those names will be placed into a drawing sometime shortly. Watch here for further updates.

**While this was initially not a numbered Grant opus, we are calling it #48 for our site count.

Sunday Surprise #1 – Contest Submissions

In addition to FoxFireX’s incredible sudoku gift that he made for someone’s birthday (some puzzles are meant to keep more private), we got three other submissions for our first Hidden Contest. We’re posting them here in increasing order of difficulty.

First up is an “Anti-Symmetry” Nurikabe from Giovanni P. where every clue that is odd/even has an even/odd clue in the corresponding symmetric place. Standard Nurikabe rules are all you need for this challenge.

Nurikabe by Giovanni P.

Solution image


Next up is a real RARITY for this website, a Shakashaka. For the general rules, we’ll direct you to where the puzzle originated. Here, Bryce Herdt has made a cipher version of the puzzle. The letters AIRTY each stand for a different number from 0 – 4 which the solver must determine.

Cipher Shakashaka by Bryce Herdt

Solution image


Finally, the hardest of the bunch, is an intriguing variation called “Sudoku Slitherlink” by its designer Scott Handelman. In addition to standard Slitherlink rules, a different number from 0-3 must go into each green cell. No number in a green cell can repeat in that row or column. As Scott warns, this is one of the hardest puzzles he’s constructed and, from his original post, he’s “still kinda shocked that the middle just kinda ‘works'”.

Sudoku Slitherlink by Scott Handelman

Solution image


All of these puzzles are grouped in this single PDF.

If you enjoy these puzzles, please comment here and say so, thanking each of the authors. As contest entries, these didn’t go through editorial review (except making sure there was a single answer), but we found them all quite interesting and worthy of being some of the first puzzles from other authors to appear on this web-site. We’re considering keeping Sunday open for “guest” submissions each week from new puzzle authors. And once we get through a stack of puzzle submissions for The Art of Puzzles, more authors will be appearing throughout the week too.

Ask Dr. Sudoku #11 – About that hidden contest…?

For the last couple weeks Sunday has been a day where we’ve seen a huge increase in page views, strictly because a new hint was released for the site’s first Hidden Contest. This led a few dedicated solvers to scour the site again looking for something out of place.

This Hidden Contest was an experiment in having “other” puzzle styles here; I’m a huge fan of puzzle hunts and secret codes and the like and was curious to see if my more observant solvers would catch onto something odd.