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.

  • Did I really use the word “kinda” twice in one sentence? How gauche.

    Both of the non-me puzzles were very enjoyable. I especially like cipher-clue logic puzzles because they feel like two puzzles in one. I even get to create a separate grid with the letters going down the side and the possibilities going across the top, like a mini version of those story logic problems that can be found at your local supermarket.

    As for the puzzle I wrote, sorry in advance, I guess! 🙂

  • Also, yes, I realize it’s not a Sudoku Slitherlink, it’s a Latin Squares Slitherlink, but that lacked alliteration.

    • Avatar photo drsudoku says:

      I didn’t want to repeat everything you said on your blog! I’m not sure, when it is not in a square shape, if even that name works. But certainly ok for your puzzle #12. Regardless, it is an interesting twist on missing clue genres.

      • Jonah says:

        It’s just a Jigsaw Extra Space Sudoku in which somebody forgot to draw the boxes but it’s solvable anyway!

        • Jonah says:

          (Technically solvable, I mean. I’ve done a lot on the outside but have no idea how to work inward.)

        • Aaron Chan says:

          Same here. I have no idea on how to begin the inner portion. Will continue later.

      • Honestly, I had forgotten that I had written the same thing on my blog. And I guess you’re right, neither “Sudoku” or “Latin Squares” really applies to this one. I think either is enough for people to understand what to do by title alone though, which is the most important thing.

  • FoxFireX says:

    Enjoyed the first two so far, and still looking for the breakin on the third. I was kind of torn about having the one I did posted, but I suppose it’s just as well to keep it down since it’s my first ever puzzle construction. (Well, other than a cryptic crossword I apparently put together when I was, like, 12 or something. Those clues were sometimes a little too cryptic, on review.) If anyone wants to have a look, I’m willing to share privately. Just email me. My username is on the top of the post, and the server is a popular Google mail service. (I’m sure you can figure out THAT puzzle!)

  • Giovanni P. says:

    I love that there are a nice variety of entries and puzzle types on this contest. Even if mine ended up being a bit easier than the others, I like the couple of stop and think moments in it. Glad people are enjoying it; I may have to get into puzzle-making mode and submit a few to the Art of Puzzles soon.

  • FoxFireX says:

    One thing I noticed is that it seems like all four entries actually submitted original puzzles for the contest. Not having created puzzles before, it was really just dumb luck that I had happened to put this one together right before I found the contest. If I’d found it a couple of days earlier, I probably would have just found a puzzle on the web, maybe one from this site, and sent a link. Would that have been good enough? Should we all plan to have a stash of ready-made puzzles on hand to submit for future contests? 🙂

    • Avatar photo drsudoku says:

      Interesting questions which I was ready for regardless of what arrived in the inbox. If you or any solver had sent a copy of one of my own puzzles, I would have given credit. I would also have then offered the chance, with the clock stopped, to re-submit an original puzzle for potential future recognition online. I did not know how many entries I would receive, so I also was prepared to simply pick extra winners from the latter submissions.

      The story of your entry was one of my favorites in the contest. FoxFireX, after many emails telling me all the places my contest was not, and identifying a couple web problems based on my shared IP hosting, randomly sent a puzzle in last Saturday. I triple-checked the address lines and also my special mailbox with auto-forwarder to be sure it was not an actual submission. On Sunday, after finally cracking the hidden puzzle, he sent it again to the right inbox.

      • FoxFireX says:

        Of course, you’re leaving out the fact that I only found the thing after deciding that I was giving up. I’d spent so long scouring the site for something, anything, and failing that I finally ragequit and sent an email saying I surrendered. After giving up, I was folding laundry when I realized there was one more place that I might hide clues that I’d never checked. Sure enough, it was exactly what I suddenly thought of. As soon as I got “EMA”, I was already convinced that I had it. I actually sent the email before I finished getting the whole message, just to try to beat anyone else.

        I was curious about what would happen if I posted that I’d found it as well; I’ve seen other contests where simply having someone finally say they’d solved it spurred other people to actually finish as well. Until you know someone has figured it out, there’s a nagging doubt that the thing is solvable. Once someone gets it, it becomes “Well I can do that!”

  • Scott Handelman says:

    Oof, I knew it was going to give people trouble. If you want some minor hints, you can e-mail me. Address is last name at gmail.

    • Avatar photo drsudoku says:

      It took me awhile to get through it and prove one solution. I learned a lot by experimentation, which let me figure out why the middle sorta works. But if I hadn’t been willing to experiment I would have been staring for a half hour at least.

    • FoxFireX says:

      Finally managed to make my way through it. That was a pretty severe puzzle for me, and I feel like Slitherlink is one of my stronger suits. Glad to have gotten it solved, regardless. Can’t have a blemish on my record for the site. 🙂

  • hagriddler says:

    Nice surprise ! Loved those contributions !
    Finally solved them all, after lot’s of attempts at the last one. I was sure I made some mistake along the way because I kept on finding contradictions, but then suddenly it solved nicely !
    Also a interesting introduction to shakashaka (what an odd name…). My neck still hurts from turning my head to toggle between perpendicular and diagonal solving… 🙂

    • hagriddler says:

      (maybe next time I’d better simply tilt my laptop) 🙂

    • Aaron Chan says:

      So there’s a nice, logical solution to the center part? I ended up using trial and error on 1 of the columns until the puzzle works.

      • FoxFireX says:

        That’s an interesting question outside of this particular puzzle, I think. I hear a lot of people talk about “logic” vs “trial and error”, but isn’t most of logic actually applying learned trial and error? It almost seems like some of the logic steps are really just being able to read ahead far enough that you find the contradiction without making a mark on the paper.

        • Avatar photo drsudoku says:

          Seems like a good Ask Dr. Sudoku topic next Sunday. I’ve certainly got a particular mind-set when it comes to Sudoku steps, but unclear how that applies to all other puzzle types.

        • Yeah, it’s a tough topic to really get a handle on. In some sense, all but the simplest forward deductions have to be proven using an indirect proof (ie, what if A? Then B, C and D. But we already know not D, so not A). For example, consider a pointing pair in Sudoku, or the 3-3 rule in Slitherlink. Try to prove any of the valid conclusions in those situations without an indirect proof (ie trial and error). So the first time you see a particular pattern, you’re probably going to be stuck doing a little trial and error, while someone who has seen that particular pattern doesn’t even do the proof anymore, they just jump to the conclusion. For the first timer, it feels like trial-and-error. For the veteran, it feels like forward logic.

          But saying that pattern recognition = forward logic while indirect proof = trial and error is a slippery slope. After all, one could say that an entire puzzle is one big pattern. The next time you see a 10×10 nurikabe with first row 3xxxx2x4x4 etc, the solution is … No trial and error needed, just pattern mapped to conclusion.

          So, what is forward logic, and what is trial and error is, in my mind at least, essentially in the mind of the solver. I tend to draw the line at proofs which involve more than one independent assumption, or with 1 assumption but more steps than I can keep in my head, and then pretty much anything of the form A -> B and not A -> B therefore B. But even that’s not a complete picture. For example, in a Kakuro puzzle, a 17/5 (sum of 17 in 5 distinct digits) clue is either 12347 or 12356 in some order. I’ll quickly eliminate 8’s and 9’s, and start looking for where the 1, 2, and 3 might go, and think of it as forward logic. But it’s clearly a A->B and not A -> B therefore B situation.

      • Bryce Herdt says:

        After my first solve, I found a simplifying rule to use in the central twelve squares, mostly the center four. It involves 0’s and 3’s, and the rest of the center can be placed by continuing to focus on 0’s and 3’s. Bigger hint?

  • Vraal says:

    The ShakaShaka was *much* easier once I stopped trying to solve it as an Akari. It… isn’t… possible as an Akari… believe me…

  • Francis says:

    Started the slitherdoku last night and got stuck, and finished it on the train this morning. Cool puzzle, though if there was a more efficient way to solve it than the one I used (which amounted to quadra-furcation), I didn’t see it. Admittedly, slitherlink is probably my worst puzzle type, logicwise.

  • Bryce Herdt says:

    If anypony’s wondering why my puzzle says “Rarity,” I explain here:

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