This is an example of a Jigsaw Sudoku. The rules of Jigsaw Sudoku are,

- Each row must contain the numbers 1-9 once, and only once.
- Each column must contain the numbers 1-9 once, and only once.
- Each sub-region must contain the numbers 1-9 once, and only once.

This particular puzzle has a 3x3 square in the middle, but all the other regions
are a non-square shape.

We can work out the value of the highlighted cell in this puzzle. We know that the top-middle region must
contain the number '1' somewhere. We can also see that the other three empty cells can't contain a '1' as
those columns already have a '1' in them. So, the highlighted cell must be '1'.

We have used exactly the same techniques as we would normally, it's just the region aren't a regular 3x3
square.

Can you work out the value of the highlighted cells using the techniques you already know? You can fill
these in right now without needing to know any more of the puzzle.