Toroidal Sudoku
Sorry for the lower quantity of puzzles this past week – I’ve been working on completing a new book so I’ve had to focus on that instead, but next week I’ll hopefully get back up to my five-a-week average! I’m not feeling very inspired in terms of being too original right now so I thought I’d post a ‘regular’ 9×9 toroidal Sudoku, although this one is a little tricky through having only 14 given numbers to start from!
As my easy and hard puzzles attest, I’ve been doing a lot of work on really accurately rating Sudoku puzzles, something which I’ve only done in a more general way before on the basis of what logic was necessary to solve a puzzle – now I can do a much more detailed analysis of the number of simultaneous possible moves at any stage of solving the puzzle, what those moves are, and at what point in the solve process they’re required. I needed this new accuracy of rating for one of my new books that will be out later this year (actually pretty soon, at the start of July), shown left – Hard-as-Nails Sudoku. It has over 200 really-difficult puzzles – they start out tricky (more than 10 minutes to solve) and end up… well, even harder than the tough puzzle I posted last week! But at no point do they use any ‘unfair’ solving logic – they stick fair and square to logic that any solver could come up with themself, without help. And of course, no guessing is ever required.
Anyway, it doesn’t take a complex analysis to see that today’s toroidal is not going to be on the easy side, given the low number of givens and the fact that toroidal puzzles really do twist things up in a difficult kind of way – so good luck! 
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about 14 years ago
Understatement coming:
THAT WAS HARD
I have done your Toroidals before, but this one really strained my eyes. I think it was because of the way the wavy regions wrapped around the corners as well as some regions having no values at all.
I got it because I was stubborn, but there were times in the solving when I wanted to just put it away and do a different “fun” puzzle.
On a positive note, if anyone needs practice scanning for X-wings, this is a good one to try.
about 14 years ago
Haha – I always find the toroidals very difficult to solve too! You don’t actually need x-wings to solve this one, I promise – in fact it’s a puzzle I made years ago, when I first started making toroidal puzzles. You don’t even need hidden sets (and I doubt you need naked sets either, but I haven’t checked to be sure). It’s mainly the twisty confusing nature of toroidal puzzles that makes it tricky.
Well done on persevering! 