## "compass" sudoku

For fans of Killer Sudoku, Samurai Sudoku and other variants

### "compass" sudoku

enxio27 wrote:

I visited the {Daily Sudoku } site,
and I have a question:
What is "compass" sudoku?
I didn't find any explanation of how it works.

Pat

Posts: 3640
Joined: 18 July 2005

### Re: "compass" sudoku

Here https://maybepuzzles.wordpress.com/types/compass/ is one definition of Compass Sudoku, though it is so obscure I am not sure this definition has anything to do with the one used by the formatter. The description also seems to be incomplete.

JasonLion
2017 Supporter

Posts: 640
Joined: 25 October 2007
Location: Silver Spring, MD, USA

### Re: "compass" sudoku

I finally figured it out. It's nothing more or less than an extra constraint puzzle in which each nonet position (upper left, lower right, center, etc.) can have only one instance of each digit. I've also seen this variation referred to as "color sudoku". Although there are a number of other color patterns in color sudoku, this one seems to be the most common.

enxio27

Posts: 460
Joined: 13 November 2007

### Re: Formatting puzzles to print and share

enxio27 wrote:Following with interest. . .

While I have your attention, I visited the site, and I have a question. What is "compass" sudoku? I didn't find any explanation of how it works.

Some 5-7 years ago, I encountered something called "Color Sudoku" in a newspaper. Each of the nine cells in a box were a different color and the addition constraint is that each color must have all digits from 1 to 9, just like the other houses (rows, columns, boxes).

While creating these color sudokus was not a big problem, it turned out that solving them on paper was hard because of the layer of color that the laser printer had applied. The ink did not stick so well.

So I went looking for a different visual representation and opted for the "Compass" flavor: Each of the cells now is assigned a direction (not surprisingly called NW,N,NE, W,Center,E, SW,S,SE) and each direction must have all digits 1-9. It is easier on the eye than those crazy colors and it is also easier to write down NW, SE than "pink", "orange"

Hope this explains what Compass is.

Why do I like the Compass puzzles so much?

They force the brain to work on one extra dimension. We are all so used to the 9x9x9 square and the well established ways of solving these puzzles.
With Compass I went back to solving with basics only (no fishy business there, no wings either), but with another "house" to keep in mind, one that is spread across the whole grid. It is MUCH more difficult to recognize a naked pair in NW than to find a quad in a Classic Sudoku row or column or box.

As I like to do my daily Sudokus at breakfast, I found out that most of the "Very Hards" with xy(z) wings take me something like 15 to 25 minutes. The Compass Sudokus usually take around 45 minutes. Basics can be quite exciting

Helmut
Nataraj

Posts: 5
Joined: 30 October 2015

### Re: Formatting puzzles to print and share

Nataraj wrote:
enxio27 wrote:Following with interest. . .

While I have your attention, I visited the site, and I have a question. What is "compass" sudoku? I didn't find any explanation of how it works.

Some 5-7 years ago, I encountered something called "Color Sudoku" in a newspaper. Each of the nine cells in a box were a different color and the addition constraint is that each color must have all digits from 1 to 9, just like the other houses (rows, columns, boxes).

Hi Helmut & enxio27,
The variant in question appears to be the variant also referred to as "Disjoint Groups Sudoko" or DG for short.

tarek

tarek

Posts: 2699
Joined: 05 January 2006

### Re: Formatting puzzles to print and share

tarek wrote:The variant in question appears to be the variant also referred to as "Disjoint Groups Sudoko" or DG for short.

tarek

Thanks! Good to know what the correct technical term is. I had no clue .

For publishing, I think I'll stick with "compass", though. Makes the whole thing less abstract, more ... tangible. More like distant exotic shores, perfect beaches, permanent vacation ... Ah, I digress.

Helmut
Nataraj

Posts: 5
Joined: 30 October 2015

### Re: Formatting puzzles to print and share

I am with different ways that present something in a clearer way. for an electronic solver to aid/help/check - gsf's, JC's & Ruud's softwares handle this variant under the DG name. There had been some puzzles of this variant posted in the "puzzles related to the patterns game" thread.

tarek

tarek

Posts: 2699
Joined: 05 January 2006

### Re: Formatting puzzles to print and share

tarek wrote:I am with different ways that present something in a clearer way. for an electronic solver to aid/help/check - gsf's, JC's & Ruud's softwares handle this variant under the DG name. There had been some puzzles of this variant posted in the "puzzles related to the patterns game" thread.

tarek, thank you for pointing me to that thread. I don't know how I missed it before, but there are a lot of interesting puzzles in there.

I understood the term "disjoint groups" to be a more general term, often used with puzzles using color blocks to designate the additional constraints, of which this "compass" variety would be a subset, or just one constraint pattern among many.

enxio27

Posts: 460
Joined: 13 November 2007

### Re: "compass" sudoku

Tarek

tarek

Posts: 2699
Joined: 05 January 2006

### Re: "compass" sudoku

I have not created any DG puzzles for a long time (and they are lost on the Djape site).

Note that the DG are orthogonal to the Nonets so you can layout a transpose puzzle with nonets as rows and DG as columns. By presenting the puzzle in two grids it makes the solving less visually taxing particularly for killer variants.

I wonder how an NC requirement in both layouts would work? I'll give it a try.
HATMAN

Posts: 213
Joined: 25 February 2006