What is a Sudoku?

Sudoku is a logical puzzle game, originally created in puzzle books and then made available in countless newspapers worldwide.
Many people are put off by seeing a grid with numbers in it, but in fact the puzzle doesn’t require any arithmetic at all – just deduction and logic.

There’s plenty of discussion about what consitutes a Sudoku puzzle, but many Sudoku fans agree:

  • A Sudoku should have 30 or less initial values filled in out of the 81 total
  • Sudoku should be solvable by entirely logical deduction – no guesses should be needed. (That doesn’t mean that you can’t use guesswork, just that you shouldn’t have to.)
  • For aesthetic reasons, a Sudoku should have rotational symmetry – the positions of the initially filled in cells should be the same if you were to turn your page round.
  • The Sudoku must only have one solution!

Of course, for beginner puzzles, often there are more than 30 values filled in – this is just to give you a head start while you’re learning!
Many people think that harder Sudoku puzzles are the ones with fewer values filled in to begin with. While this is often the case, there are plenty of frustratingly difficult puzzles available with 28 or more cells filled in – difficult because they really require you to use lots of different solving techniques to complete them.

Click here if you’re interested in the technical aspects of how we create and rate Sudoku!

Why Do Sudoku?

Lots of reasons!

  • Playing Sudoku engages the brain
  • It can be relaxing, but challenging – you choose the level you want to play at!
  • It increases concentration and focus
  • For some people it can be as helpful as meditation in improving relaxation and calmness
  • It improves your logic and memory
  • Studies have shown that using the brain for puzzles such as Sudoku and Crosswords helps to slow the effects of dementia and alzheimers
  • You can play a Sudoku puzzle a bit at a time, you don’t have to do it all at once, so it’s ideal if you’re likely to be interrupted
How Do I Get Started?

We’ve put together an absolute beginner set of puzzles and some help on how to get started!