This is a magnetic dominoes puzzle, a hybrid of the Magnets and Domino types that frequently appear at WPCs. Detailed rules follow below the image.
(Click for larger size)
Rules
- Fill in the grid with numbers from 1 to 6 (some numbers are given), and then partition the grid into 1 by 2 dominoes oriented in either direction so that all 21 possible dominos with numbers from 1 to 6, including doubles (1-1, 2-2, etc.), appear.
- Two adjacent numbers may be equal only if they are part of the same domino. In particular, there will only be six pairs of adjacent squares with equal numbers, corresponding to the six double dominoes.
- If one marks the greater number in each domino with a plus and the lesser number with a minus, no two plusses or minuses can be adjacent, as in the Magnets type. Double dominoes with two equal numbers are non-magnets and are not marked with a plus or a minus.

July 1, 2011 at 10:43 am |
This was really tricky. I think I’d have solved it a lot faster with a little bit of trial and error, but thankfully this is not a contest. Thanks!
July 2, 2011 at 3:54 pm |
It took me forever to see the break-in, but it was well worth it. Two difficult steps, and then it flowed very nicely.
August 1, 2011 at 5:38 am |
Likewise, I stared for a long time, and the break-in was very satisfying..
Helpful hint to anyone stuck, painting ‘plus’/'minus’ is handy..
September 12, 2011 at 2:36 am |
I *think* I have a possible break-in on the left with the 1-2-6 column, but can’t seem to convert it to an actual solution.
September 12, 2011 at 2:38 am |
That 1-2-6 is just one part of how you get started.