March 04, 2011

Friday Puzzles #94

Don’t Masyu look so much better with a nice bit of symmetry!? This week’s puzzle would probably count as a medium if it were 10×10 rather than 18×10 – but perhaps that’s only because I don’t believe you can have a hard 10×10 Masyu. I’d say it’s definitely hard by nikoli.com standards. Included in this puzzle is a twist on an old chestnut, which nevertheless I haven’t seen before. Maybe I’ll send it to 11 some other time. Still, I reckon this puzzle isn’t so bad either. Enjoy!

#120 Masyu – rated hard

All puzzles © Tom Collyer 2009-11


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  1. Warren

    I wouldn’t say it was hard (maybe on the border). I’ve only done a handful of Masyus, mainly thanks to your blog for me getting into them and understanding them better, and I found it pretty straightforward with only one or two points where I had to stop and think for a few seconds.

    Nevertheless, I found it a very smooth puzzle and, once again, excellently constructed.

    04 Mar 2011, 14:07

  2. Without wanting to give the game away too much, I can’t see where the left solve of the puzzle can be resolved by anything other than noticing the trick I was going on about, and that’s certainly non-trivial. Although I do agree that forcing symmetry onto a puzzle does mean that it is quite easy in places simply to force the solution to be unique!

    04 Mar 2011, 14:21

  3. Warren

    I did make an assumption that the solution was unique which helped me speed though. And I’m sorry to say that I didn’t notice your trick – although that’s probably more to do with me not doing Masyus often.

    Maybe you can write a book on them akin to Thomas Snyder’s wonderful TomTom book which I’m currently working my way through and is thoroughly delightful :)

    04 Mar 2011, 15:00

  4. Ah fair enough. As the author, I’m afraid I have to disregard any uniqueness strategies (or else how do you know it solves uniquely in the first place ;) ), and this is taken into account with my ratings…

    05 Mar 2011, 01:44

  5. MellowMelon

    If your trick has nothing to do with the themed step in this one (http://mellowmelon.wordpress.com/2010/03/07/puzzle-207/), then I missed it too.

    05 Mar 2011, 04:46

  6. MellowMelon: yes I think it does – or at least something equivalent – assuming you referring to doing things to avoid a loose strand being trapped in a cul-de-sac. Although there are plenty of goodies in that puzzle! What I am referring to is a specific configuration of four circles which forces a couple of deductions.

    Actually, to reply to email correspondent Jeffrey H and presumably to lots of other readers you could by-pass this configuration with a little bit of “painting”, as was pointed out to me in this email. I think what I’ll have to do is send it to 11 to make sure everyone gets the point next week!

    05 Mar 2011, 19:50

  7. Jeffrey

    Thanks for your reply. Enjoyed the puzzle, and looking forward to the follow-up :)

    06 Mar 2011, 03:03


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Welcome to the blog of current UKPA sudoku champion, two-time Times national sudoku champion and general logic puzzle fan Tom Collyer.



Home of the original Friday Puzzles, each Friday I publish a 100% original and handmade logic puzzle, inspired by the world-famous Nikoli company.


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AkariFillominoHashiHeyawakeHitoriKakuroLITSMasyuNumberlinkNurikabeRipple EffectShikakuSlitherlinkSudokuSuraromuYajilin.

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