There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l 3 l _ l 6 ll _ l _ l _ ll _ l _ l 2 l
l _ l _ l 4 ll 8 l 6 l _ ll _ l 9 l _ l
l 1 l 9 l _ ll _ l _ l _ ll 3 l _ l _ l

l _ l _ l _ ll 6 l 9 l _ ll _ l 5 l 7 l
l _ l _ l 1 ll 2 l _ l 4 ll 9 l _ l _ l
l 8 l 6 l _ ll _ l 3 l 5 ll _ l _ l _ l

l _ l _ l 8 ll _ l _ l _ ll _ l 7 l 1 l
l _ l 5 l _ ll _ l 4 l 8 ll 6 l _ l _ l
l 6 l _ l _ ll _ l _ l _ ll 4 l _ l 9 l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l _ l 7 l 6 ll _ l 9 l 5 ll _ l 2 l _ l
l 1 l _ l 8 ll 3 l _ l 4 ll _ l 7 l 9 l
l 4 l _ l 5 ll 1 l _ l 2 ll 6 l _ l 8 l

l _ l 6 l _ ll _ l 4 l 1 ll _ l 8 l 5 l
l 9 l 5 l 2 ll _ l 3 l _ ll 4 l 6 l 1 l
l 8 l 4 l _ ll 5 l 2 l _ ll _ l 9 l _ l

l 6 l _ l 9 ll 2 l _ l 7 ll 8 l _ l 3 l
l 2 l 8 l _ ll 4 l _ l 3 ll 9 l _ l 6 l
l _ l 3 l _ ll 6 l 8 l _ ll 7 l 1 l _ l

Also, is there any standardized technique or algorithm (by hand or using some open-source code) for creating Sudoku tables according to a wished level of complexity? Or is there no other way to do it than through a lot of trial and error? Also, how do you know whether you’ve stumbled upon a brand new combination? Is there a list somewhere on the Internet with tried and tested combinations?

One final question, how would you qualify this game below (and why)? Medium? Obviously, it’s not as easy as some others that I’ve tried in that it cannot be solved simply through the filled in blanks alone. But it was not extremely hard either and I can’t imagine there not being anything harder…

l _ l _ l 7 ll _ l _ l _ ll 3 l 5 l 4 l
l 8 l _ l _ ll _ l 1 l _ ll _ l _ l 9 l
l _ l 5 l _ ll _ l _ l 4 ll _ l _ l _ l

l 5 l _ l _ ll 4 l _ l _ ll 9 l _ l 8 l
l _ l 3 l _ ll 9 l 6 l _ ll 1 l _ l _ l
l 9 l _ l _ ll 5 l _ l _ ll _ l 2 l _ l

l 2 l _ l _ ll _ l 3 l _ ll 4 l 8 l _ l
l _ l _ l 3 ll _ l _ l 8 ll _ l _ l 6 l
l _ l 8 l 9 ll 2 l _ l _ ll _ l _ l _ l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l 9 l _ l 6 ll 5 l _ l 3 ll _ l _ l _ l
l _ l _ l 3 ll 8 l _ l 7 ll _ l 5 l _ l
l _ l 7 l _ ll _ l _ l _ ll 3 l _ l 1 l

l 3 l 2 l _ ll _ l 7 l _ ll _ l _ l _ l
l 8 l _ l _ ll _ l 4 l _ ll _ l _ l 9 l
l _ l _ l _ ll _ l 8 l _ ll _ l 1 l 2 l

l 4 l _ l 9 ll _ l _ l _ ll _ l 2 l _ l
l _ l 3 l _ ll 1 l _ l 4 ll 5 l _ l _ l
l _ l _ l _ ll 6 l _ l 2 ll 4 l _ l 8 l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l _ l 6 l _ ll _ l _ l 5 ll 4 l 3 l _ l
l 1 l _ l _ ll _ l 3 l _ ll 6 l _ l _ l
l _ l _ l 9 ll 4 l 1 l _ ll _ l 8 l _ l

l _ l _ l _ ll 2 l _ l _ ll 8 l _ l 9 l
l 4 l _ l _ ll 7 l _ l 1 ll _ l _ l 3 l
l 3 l _ l 6 ll _ l _ l 9 ll _ l _ l _ l

l _ l 8 l _ ll _ l 2 l 7 ll 1 l _ l _ l
l _ l _ l 5 ll _ l 9 l _ ll _ l _ l 8 l
l _ l 7 l 3 ll 1 l _ l _ ll _ l 4 l _ l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l _ l 1 l _ ll 2 l _ l _ ll _ l 4 l 6 l
l _ l 9 l _ ll _ l 7 l _ ll 3 l _ l _ l
l _ l 3 l _ ll _ l 4 l 9 ll 1 l _ l _ l

l 6 l _ l _ ll _ l _ l 4 ll 2 l _ l _ l
l 1 l _ l 9 ll _ l _ l _ ll 4 l _ l 5 l
l _ l _ l 5 ll 7 l _ l _ ll _ l _ l 3 l

l _ l _ l 2 ll 5 l 1 l _ ll _ l 8 l _ l
l _ l _ l 8 ll _ l 6 l _ ll _ l 2 l _ l
l 7 l 6 l _ ll _ l _ l 8 ll _ l 3 l _ l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l 8 l _ l _ ll _ l _ l 9 ll _ l 5 l _ l
l _ l _ l 5 ll 3 l 1 l _ ll 8 l _ l _ l
l 6 l 3 l _ ll _ l _ l 4 ll 1 l _ l _ l

l _ l _ l _ ll 2 l 7 l _ ll _ l _ l 4 l
l 5 l 6 l _ ll _ l _ l _ ll _ l 2 l 8 l
l 7 l _ l _ ll _ l 4 l 6 ll _ l _ l _ l

l _ l _ l 9 ll 4 l _ l _ ll _ l 7 l 1 l
l _ l _ l 6 ll _ l 9 l 2 ll 4 l _ l _ l
l _ l 1 l _ ll 7 l _ l _ ll _ l _ l 9 l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l _ l _ l _ ll _ l 4 l 1 ll _ l _ l 9 l
l 8 l _ l 3 ll _ l _ l _ ll 7 l _ l _ l
l 2 l _ l _ ll _ l _ l 5 ll 6 l _ l _ l

l _ l 3 l _ ll 7 l 5 l _ ll _ l 8 l 2 l
l _ l 2 l 8 ll _ l _ l _ ll 5 l 9 l _ l
l 5 l 6 l _ ll _ l 2 l 8 ll _ l 3 l _ l

l _ l _ l 2 ll 6 l _ l _ ll _ l _ l 4 l
l _ l _ l 7 ll _ l _ l _ ll 9 l _ l 3 l
l 9 l _ l _ ll 4 l 1 l _ ll _ l _ l _ l

There are 9 rows of numbers across and 9 columns of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row, column, or 3×3 square.

l _ l _ l _ ll 1 l 5 l _ ll 2 l 3 l 9 l
l 2 l _ l _ ll 6 l 9 l 8 ll _ l _ l _ l
l 7 l _ l _ ll _ l _ l 2 ll _ l _ l _ l

l 9 l _ l _ ll _ l _ l 3 ll 5 l 6 l _ l
l _ l 6 l _ ll _ l _ l _ ll _ l 7 l _ l
l _ l 7 l 2 ll 9 l _ l _ ll _ l _ l 8 l

l _ l _ l _ ll 3 l _ l _ ll _ l _ l 7 l
l _ l _ l _ ll 2 l 8 l 9 ll _ l _ l 4 l
l 4 l 2 l 3 ll _ l 7 l 6 ll _ l _ l _ l

There are 9 rows of numbers across and 9 rows of numbers down.
Numbers 1 through 9 need to go across and down.
You can only use each number once in each row.

l _ l 3 l _ ll 6 l 2 l 4 ll 8 l _ l 1 l
l _ l 6 l _ ll _ l 8 l _ ll _ l _ l 4 l
l _ l 8 l _ ll 7 l _ l _ ll _ l _ l 9 l

l _ l 9 l _ ll 4 l 7 l _ ll _ l _ l _ l
l 4 l _ l _ ll _ l _ l _ ll _ l _ l 7 l
l _ l _ l _ ll _ l 6 l 3 ll _ l 9 l _ l

l 3 l _ l _ ll _ l _ l 6 ll _ l 4 l _ l
l 6 l _ l _ ll _ l 5 l _ ll _ l 1 l _ l
l 7 l _ l 1 ll 8 l 4 l 2 ll _ l 6 l _ l