813554 wrote:It always surprises me how easy it is... Thank you. I don't understand how you people can see it this easy, in fact you make it seem too easy so I don't understand how I couldn't see it. Thank you again.
It gets easier with practice. In fact, this is a good puzzle for learning about the easiest single-digit chains, because most variants (Skyscrapers, 2-String Kites, Empty Rectangles, and other unnamed Turbot Fishes or generic X-Chains) can be found on the same cluster of 9s. Some of them can also be seen as Finned or Sashimi X-Wings, which is another point of view of the same eliminations. I recommend that you save this puzzle and try to find as many variants of those single-digit patterns as you can.
At first it's probably hard to see the patterns directly, but you can cheat by using Simple Coloring, when you notice a certain digit has lots of bilocation strong links (i.e. just two instances in a box, row, or column). For example, here I've "colored" the interesting cluster of 9s with ' and " to depict the two opposing parities:
- Code: Select all
.-------------------.----------------.---------------------.
| 7 59 13 | 13 6 59 | 248 248 48 |
| 2 15 8 | 7 15 4 | 9 3 6 |
| 4 39 6 | 8 2 39 | 5 1 7 |
:-------------------+----------------+---------------------:
| 5 13 13 | 9 4 8 | 7 6 2 |
| 6 48 4(9") | 2 57 57 | 3 8(9') 1 |
| 8(9') 2 7 | 6 13 13 | 48 5 48(9") |
:-------------------+----------------+---------------------:
| 389 4678 2 | 13 13789 137 | 1468 4789 5 |
| 1 678 5 | 4 789 2 | 68 789 3 |
| 389 478 4(9') | 5 13789 6 | 1248 24789 48(9') |
'-------------------'----------------'---------------------'
Notice the bottom row which has two 9s with parity '. That's a contradiction ("color wrap"), which means we can eliminate all 9s of that parity (r6c1, r5c8, r9c3, r9c9) and place all 9s of the opposite parity (r5c3 and r6c9). We can also see individual elimination possibilities using "color traps", i.e. when a candidate sees both parities it can't be true. That applies to r9c3 and r9c9 here, but those eliminations are already covered by the more powerful color wrap so they're redundant.
Now that you know what can be eliminated, you can (and should) try to see how each of those eliminations could be spotted and described as individual patterns or chains. That's how you eventually learn to see them directly as well, and can choose surgical strikes (patterns, chains) instead of weapons of mass destruction (coloring).
Notice that Simple Coloring is the weakest of coloring techniques and only shows pretty obvious eliminations (i.e. they become obvious once you get more experience). To see more, you need more powerful variants such as X-Coloring, 3D-Medusa, or GEM.