In this type of puzzle we are asked to fill in the numbers 1 to n on every row, in every column and in every area of n cells, bordered by a thicker line. Next to the puzzle, the number n is given.

Some puzzles have highlighted diagonals, indicating these also needs to contain n different digits. In some variants different puzzles overlap.


As an example we will show how to complete a smaller grid with only the numbers 1 through 4.

In the leftmost column the 1, 2 and 4 are given. So we can write the only one left out, the 3, int he only empty box. In the larger square in the upperleft we have also got little choice, so there we will put a 2.

By having entered the 2, now suddenly for the value in the third square of the first row only one value remains, a 3. And in the same manner we subsequently complete the third column and the second row.

How to finish the job? Well, on the third row only 2 and 4 are missing, but the 4 is no longer welcome in the rightmost column ever since we completed the second row, so we write the 4 in the second column and the 2 in the fourth. The remaning two digits follow naturally.


This genre was invented by Howard Garns back in 1979 by whom it was called "Number Place". Only since 1986, when puzzle publisher Nikoli spread it in Japan, it became known under its current name, which means something like "independent numbers".

World champions
2006: Jana Tylova (Czech Republic)
2007: Thomas Snyder (United States)
2008: Thomas Snyder (United States)
2009: Jan Mrozowski (Poland)
2010: Jan Mrozowski (Poland)

Puzzles in this genre.