Think you've mastered Sudoku? our expert explains what makes Hard Sudoku more challenging and whether you're ready to take the next step.
So you’ve played a few dozen games of Sudoku and you’re confident that you’ve got the basics down perfectly. You know how to slice and dice your grid, and you know how to fill an almost empty playing field with the correct numbers in the space of a few minutes.
Maybe you’re now looking for a bit of an extra challenge. And maybe Hard Sudoku is just what you’re looking for. But just how hard is it really? Are you ready to make the leap?
The most important thing to understand is that Hard Sudoku doesn’t add any new rules to the game. It’s the same Sudoku you’ve been playing up until now.
You’re still dutifully filling a 9x9 grid with numbers. And you’re still making sure that the numbers one through to nine appear once in every row, every column, and every marked out 3x3 square. And you’re still doing all of this by working out what the numbers you’ve been given mean for the various blank squares on the grids.
Hard Sudoku is harder because it gives you fewer clues. This either means that there are fewer numbers on the board at the start, or that the numbers you have been given don’t allow for such easy solving.
Rest assured, though, there is still a right and a wrong solution for every empty square in the grid. And Hard Sudoku is still scrupulously fair. It still gives players a route from the start of the game right through to the end. That route’s just a bit harder to see.
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This one is crucial. Every game of Hard Sudoku is timed, but you don’t really have to worry about that.
At first, when you’re still getting your bearings, just ignore the amount of time you’re taking to fill in the grid. Enjoy the process itself with no additional pressure.
Scan the grid for as long as it takes: there will always be one number that’s a bit easier to work out than all the others. To find promising locations, look for numbers that crop up an awful lot. If there are a lot of eights already, chances are good you’ll be able to fill a few more of them in, as you’ll have more information on their placement.
Also, look for busier parts of the grid. The more squares that are filled in already give you more clues as to the squares that remain empty.
This is true of normal Sudoku games, but it’s even more important now. Each number you place in a square changes the entire board, so keep scanning the rows and columns to see if you’re creating any new solving opportunities for yourself.
Also, if you’re stuck in one part of the board, just pick another spot. Go where your eye takes you. There might be something that you’ve almost noticed that has drawn your attention.
With Hard Sudoku it’s more important than ever that you use the pencil tool to put in any potential numbers you’ve narrowed a square down to. This is because there’s a lot more uncertainty for you to keep track of in Hard Sudoku, particularly at the very start of a game.
Any squares you’ve narrowed down to two or even three potential numbers are a few steps closer to being solved.
The hint button is there for a reason. It will keep you moving when you’ve run out of other options. Equally, don’t be afraid to check the placement of the numbers you’ve put down already.
This won’t just tell you where you’re going wrong, it will also confirm the numbers you’ve correctly entered. And it allows you to look at the whole board afresh and maybe see some patterns you’ve not spotted until now.
You spend a lot of Sudoku thinking about where that crucial 7 might end up. But it’s just as important to flip it and see where it can’t go.
If an entire row of the 3x3 grid above you is already filled and there’s no seven in there, you have narrowed your sevens placement down to the remaining two rows. And that’s even before you’ve looked up and down to see if they already have sevens in them.
The harder Sudoku puzzles encourage you to rule out as many squares as you rule in.
If you’re really stuck and you already have a good few numbers on the grid that you’re sure of, you can always try this simple strategy: stick a number into an empty square completely randomly and see which of the game’s rules it breaks. If it leads to too many 6s in a row or column, you can rule another 6 out, for example.
This kind of creative approach to problem solving is the kind of thing you probably didn’t need to rely on in normal Sudoku. But in Hard Sudoku you’re encouraged to be more creative. That’s why it’s harder, and it’s also why it’s more satisfying.
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