Signdoku

Signdoku is a killer sudoku variant, in which the box constraint is dropped, and cages do not have to contain unique number combinations (e.g. 2,4,2 is valid in signdoku). And one other thing - a whole range of maths operations is allowable, that is +, -, x and even divide (symbolised with /).

Signdoku appears to have a huge range of different names, however on looking at a few web pages it appears that most of these are trademarked and hence we are calling it signdoku here which seems to be one combination not used elsewhere (things like kenken and kendoku are trademarked which is the name under which a puzzle with these rules is often published).

The puzzles can be any size, the most common in publication appears to be a 6x6. Here is a 4x4 puzzle, and we've included a couple of values to give you a head start. Colour demarcates the coloured regions.

7+	8x		3+
	3+
1-	2x 1	12x 3	12x