Dr. Sudoku Prescribes #80 – Masyu (Deformable)

Masyu by Thomas Snyder


or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between linex mode where left click+drag draws lines and right click marks X’s and a black circle shading mode.)

This is a “Franken-Friday” puzzle variation.

Theme: This is not all white!

Rules: Standard Masyu rules. Also, some white circles must be shaded in to become black circles to allow solution of the puzzle.

Answer String: Enter the length in cells of the horizontal loop segments from left to right in the marked rows, starting at the top. If the loop only has vertical segments in the marked row, enter 0. Separate each row’s entry with a comma.

Time Standards (highlight to view): Grandmaster = 6:00, Master = 9:00, Expert = 18:00

Solution: PDF

  • Ravi says:

    Wow I can’t believe that I have made it to Grandmaster time.
    The puzzle construction is very much straight forward with 2-3 pauses (at least for me).


  • Para says:

    Very lenient Grandmaster time. Once I understood the diagonal rule that keeps applying here, it went really quickly.

    • Avatar photo drsudoku says:

      It’s not like I just pull these times out of thin air; I had six testing times, from 6:04 to 12+. (Note to self — run a test where one week I just pull these times out of thin air.)

      I do feel this variation really is one where Masyu constructors will shine, perhaps because when you construct a theme you often think “well this will be a circle but I don’t know which color yet” so you can know a lot about cornering around circles and such.

      • Para says:

        Yeah, I know. I was just commenting from my personal solve. It wasn’t meant as a complaint. There will always be puzzles that might slip by and cause trouble for all your test solvers, while many other solvers will get through them much easier. It’s a statistically unavoidable. It can hardly be avoided unless you want to set up a group of 1000 test solvers. We all have happen in competitions that high scoring puzzles solve quickly for us, while other lower scoring puzzles take us far longer than they should.

  • I often print puzzles out and carry them around with me for a time when I have some spare minutes like a long train ride, so it’s very helpful for the special rules to be included in the PDF. Thanks!

    This one took me about 10 minutes and it was a lot of fun. I felt like I found a few useful logic steps that could be re-used in several places, which made me feel like I was really learning something as I went.

  • chaotic_iak says:

    03:48. Wait…

    For some reason I don’t consider this harder than a Wednesday. Perhaps because you’re forced that you can only put variations on Tuesdays and Fridays only?

    The configuration is pretty neat; the box and the diagonal in the center. Is that diagonal intentional?

    • Avatar photo drsudoku says:

      I was trying for mostly diagonal symmetry (LL-UR) and began with the 6×6 box and an intention to fill it with some off diagonal lines too. The final puzzle ended up with “2 extra” circles to give it a non-symmetric solve.

    • James McGowan says:

      I like having a Grandmaster time that I can beat occasionally. I think Thomas is right, being familiar with this type of puzzle makes a big difference to the time.
      If you want a harder version, I made a bigger one (and a smaller one) for the UK Open tournament last month:

  • skynet says:

    Thnks motris.You made me just construct a partial Masyu puzzle.

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