Countdown Tapa: 8 Days to Go

To enable our June reopening, Serkan Yürekli has stepped into a role as Managing Editor for the site. Serkan now oversees our puzzle submission and review process, assembles the web weeks, and has also brought new ideas for puzzle packet formatting, books, and other things you’ll see as we re-launch. As one small example, while we have always had an escalating set of puzzle difficulties from Monday to Saturday, we are now going to try to put star ratings (out of 5) on all puzzles for more comparison across weeks. We’re quite excited to have Serkan step into this larger role, and hope it increases the quantity of puzzles we can release without any change in the quality you have come to expect from GMPuzzles.

Enjoy this challenging Tapa (False) variation from Serkan as we count down the 8 days remaining.

Tapa (False) by Serkan Yürekli


Theme: 8 (or 2 cubed)

Author/Opus: This is the 280th puzzle from our contributing puzzlemaster — and new managing editor — Serkan Yürekli.

Rules: Variation of Tapa rules. All clue digits are false and should be either one higher or one lower than the value given. (Note: Some corrected clue sets may be identical to their uncorrected versions, e.g. 1 2 becoming 2 1. Some corrected sets may contain zeroes, which have no effect on the remainder of the clue set.)

Solution: To be posted next Sunday (May 31).

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

Countdown TomTom: 15 Days to Go

June 1st will be the reopening of GMPuzzles. In recent years we have had on weeks and off weeks, but with this relaunch we are planning to have content every week. Monday through Saturdays will be new puzzles, with increasing difficulty throughout the week. There will be a mix of variety weeks and single puzzle genre weeks. On Sundays we will be releasing solution images for all of the puzzles, as well as a solution video walkthrough for one of our puzzles. While these solutions have historically been “rewards” for our subscribers, we hope that sharing them more broadly will help expand our community and help people learn how to solve our hardest puzzles.

We’ll have info on some other changes soon; for now, enjoy this Countdown TomTom.

TomTom by Thomas Snyder


Theme: Countdown + 15 Spirals

Author/Opus: This is the 357th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard TomTom rules, using the integers 1-8.

Solution: PDF.

Note: Follow this link for other TomTom. 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 Art of Puzzles, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

GMPuzzles: Countdown to Reopening

It has certainly been a challenging start to 2020, but we’re excited to announce that we will be back with daily content starting in June. More info soon; for now, enjoy this Countdown Star Battle.

Star Battle by Thomas Snyder


Theme: 22 Stars for 22 Days

Author/Opus: This is the 356th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: Standard Star Battle rules. Two stars per row, column, and region.

Solution: PDF.

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

Swivelling Serpents [Birthday Surprise] by Prasanna Seshadri

(Note: This bonus puzzle is being posted today to mark the occasion of Prasanna’s birthday.)

Swivelling Serpents by Prasanna Seshadri


Theme: One Away from Thirty

Author/Opus: This is the 180th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: Locate two snakes in the grid. Each snake must start from one of the gray circles, but has an unknown ending point. Black circles represent an interior cell of one of the snakes, and all black circles must be part of a snake. Each snake’s path is allowed to move vertically, horizontally, or diagonally between cells. An interior snake cell can only be adjacent to two other snake cells (including diagonally adjacent cells) and an end of the snake can only be adjacent to one other snake cell (including diagonally adjacent cells). The two different snakes must not share any adjacent cells.

There are some numbers outside the grid. These numbers indicate the number of vertical or horizontal edges (not corners) that snakes cross in that direction.

There are some letters inside the grid. For each distinct letter, exactly one of its instances is visited by one of the two snakes.

Also see this example:

Swivelling Serpents Example

Solution: PDF

Pentominous ebook and another update

Dear solvers,

We just added the Plenty o’ Pentominous 2 ebook from Grant Fikes and Murat Can Tonta to our web store. These two fantastic authors have constructed 53 more creative Pentominous puzzles including some new highly original themes. So if you enjoyed their first Pentominous collection (or even, on the other extreme, if you’ve never solved a Pentominous before) you may want to check out this new book.

While I don’t have another update on when GMPuzzles will begin posting web puzzles again, that is in part because of a different, non-puzzle update from me. After almost five years at Verily Life Sciences (formerly Google), most recently as the Head of Computational Biology, I just left that job. I will be returning to Adaptive Biotechnologies as VP/science lead for their immunosequencing diagnostics program in early March. I’ll be splitting time in Seattle and San Francisco for this new role, and it will be the main focus of my time for the next several years. (I’m still hopeful that if I can successfully hand off most GMPuzzles responsibilities to others in the coming months, this should not have too large an effect on this site going forward; thanks again for your patience as I work through this life transition.)

A/B Testing

Dear friends,

This weekend is the MIT Mystery Hunt and Grandmaster Puzzles is very happy to be a sponsor of this puzzle event in 2020.

If you are new to this site, there are lots of different fun genres of logic puzzles to explore and you can follow some of the links to the left to find these genres including our easiest puzzles to get started. The Intro to GMPuzzles and Logic Puzzles 101 books are some great titles to try as well.

As part of the pre-Hunt activities for the team I compete with, I created the attached puzzle set in the style of a Mystery Hunt puzzle. Like most puzzlehunt puzzles, it is missing some of the instructions you may want to have but I think you may still be able to figure it out. It has a final answer which is a word/phrase. We will post some hints and/or the answer in the coming weeks.

Puzzle PDF for A/B Testing

Teaser image 1 = Framed!:

A/B Testing by Thomas Snyder

Teaser image 2 = Easy as 1, 2, 3:

A/B Testing by Thomas Snyder

Update on GMPuzzles

I’m sharing here a message I sent to subscribers by email this weekend, which contains a lot of the emerging vision I have for 2020 and beyond. We’ll be back soon (but with no fixed date in 2020 for this return yet), but I’m excited for what is coming.


TL;DR: I’m writing to share an update with what should be good news as we will be back sometime in 2020, but with some immediate changes including the end to all subscriptions in their current form.

Dear subscribers,

As mentioned a few months ago, my full-time work in science and my goals for bigger things for GMPuzzles made it unsustainable to continue to do regular web puzzle posting, e-book publication, as well as routine subscriber reward fulfillment. It was not an easy decision to “pause” the site, but the words of encouragement from you — our loyal fans — have helped over November in clarifying our best approach to 2020 and beyond.

A couple common themes that you shared with me were that:

  • Many of you subscribed in part to just give back to a site that you loved (that you’d donate if you could and that I shouldn’t bother to send a refund*).
    • *I am still going to send you a refund for any 2020+ prepayments by end of year, as that is what any business should do in this situation.
  • The solving videos really helped you better understand the puzzles, author motivations, and tips to solve them. They were one of your favorite rewards.

Across these themes and others was a pretty clear signal that we have the right content (elegant hand-crafted puzzles from our group of authors) but the wrong approach at the moment for this content, particularly the wrong early monetization. The Patreon/subscriber reward type model was a first experiment but one that it is time to end. It makes it harder to do our job each week. A lot of the interactions because of the small scale have not been automated, like adding/subtracting names from the email list. Rewards that need me to reach out 2 or 3 times for a book choice (and I still am bothered when 15% have an unclaimed reward even after many messages). So when subscriptions after a couple years do not bring in too much revenue (and I don’t need the revenue at the moment to keep the site running for many years), I should return to focusing on the core strengths. One of my biggest regrets in going to the subscription model is that it greatly reduced the commenting on the GMPuzzles blog. We never had a technical solution to let you comment early when receiving the puzzles early, so the discussion from those who would print a puzzle out after 9 AM to do that day died away. I think it is important to have “events” to build a community like first releases to everyone at the same time, as well as other time-scale releases (products/books) that aren’t meant to be absorbed in the same way.

Building the puzzle community is the most important thing we should be doing right now. Our solving videos on Youtube are another important channel we’ve not tried to make the main channel. That is where I want to start an active web channel for me and other puzzlemasters who solve our GMPuzzles posts (and possibly outside puzzles like Puzzle Grand Prix puzzles) to discuss the beauty of puzzles as a means to *grow* a community, including a competitive puzzle community. Putting all the videos *behind* the paywall is a mistake I need to undo. I am going to unhide the whole channel very soon. I’ve already shared the full backlog of videos with you a couple weeks ago. I’m sharing it with the world, and going forward it is not a “reward” to learn how to solve a puzzle. It is a route into our community for people of any skill level.

So in 2020 (but not in January), we’re going to return to a predictable web posting schedule. We will add solutions in PDF form to each puzzle after a few days so that we can cut down on the only comments we still routinely get on the site that need moderation — people doubting we have a valid or unique puzzle solution (and we’ve never made an error *yet*). And we’ll probably completely remove the puzzle submission tracker but not the rating/fave system as it takes us extra work to define submissions, add arrows to our otherwise automatically generated art, and triple check we don’t have typos there (where again we have many checks on the puzzles but not the submissions). Keeping the good pieces and making them easier to get to you, with a focus on growing the audience, is the core theme for 2020. And I have a very good candidate (you may be able to guess who) for our Managing Editor position who will come on in January to ensure we have this predictability in all things GMPuzzles when we “unpause”.

As a business, we will still try to generate some revenue, by publishing and selling e-books. Once we get a routine schedule for these books to be published, including regular series we are launching like Grandmaster Puzzles Quarterly, we may turn on subscriptions again to let you receive some of our books at a discount. But we will have a far better technical solution for how to get you that content so that it can actually scale.

For seven years since launching the site, I’ve considered myself the main patron of GMPuzzles. I have put both time and money into seeing the puzzles I like to solve come about more. I’ve appreciated having other patrons take off some of this burden (financially), but the burden in time was actually larger than expected in doing so. So I’m improving the patronage goal by simplifying too. We will add a tip jar to the site. And we will let you choose whether you want to donate to GMPuzzles, to a puzzle author, or to both at some ratio. GMPuzzles is stronger than just me, and you should have a way as we grow the community of puzzle authors alongside the community of puzzle solvers to encourage their art.

While this is a long message, I want to close the mail with a simple message of thanks. For as much as you’ve thanked me for our puzzles, I am as appreciative of the thoughtful comments, patience, and dedication you’ve shown me and the site over the years. I would not find the energy to continue to try to make GMPuzzles a larger thing if not for all of you!