Jigsaw and irregular sudoku

Jigsaw sudoku and irregular sudoku seem to be the same thing!

With jigsaw or irregular sudoku, what is irregular is the shape of the 3 x3 boxes that you get in standard sudoku.

These are changed into all sorts of shapes, and the rule still holds that the rows and columns contains 1 to 9 once only, but the twist is that the 3 x3s are warped into all sorts of shapes, and therefore ensuring that these regions have the numbers 1 - 9 once only is quite hard.

It's probably best illustrated with an example of an online jigsaw sudoku here:

[a http://www.saidwhat.co.uk/puzzleclub/jigsaw/ [/a]