Technique lessons
Every sudoku technique, explained.
Eight techniques are enough for almost every puzzle, and each one assumes the ones before it. Every page here says what the technique does, walks through a worked example, and tells you how to spot the pattern while you are solving.
The eight techniques.
In the order the game's lessons teach them, from the move that needs no looking ahead to the one that needs you to follow a digit across the whole grid.
- 01
Single candidate
The last digit a cell can take, found by counting what its row, column and box already hold.
Beginner - 02
Hidden single
A digit that fits in only one cell of a unit, even though that cell can take others too.
Beginner - 03
Locked candidates
A digit trapped in one line inside a box, or one box inside a line, that can be removed elsewhere.
Intermediate - 04
Naked pair
Two cells in one unit with the same two candidates, which rules those digits out elsewhere.
Intermediate - 05
Hidden pair
Two digits that can only go in the same two cells, crowding out everything else in them.
Intermediate - 06
Naked triple
Three cells in one unit whose candidates together come to exactly three digits.
Advanced - 07
Hidden triple
Three digits that can only go in the same three cells, clearing the rest of the candidates from them.
Advanced - 08
X-Wing
A digit with two homes in each of two rows, and both rows sharing the same two columns.
Advanced
Where to start.
Begin with single candidates. Most of a puzzle falls to them alone, and everything later assumes you can spot them without thinking. Hidden singles come next, then locked candidates: those three carry the ordinary difficulty levels from start to finish.
The pairs and triples are for puzzles that have stopped moving. They remove candidates rather than placing digits, so the reward arrives a move or two later. X-Wing is the last of them and the rarest, and it is the first that asks you to follow one digit across the whole grid instead of reading a single cell.
Practise them in the app.
Each lesson opens with a worked example and then gives you three puzzles of its own, so a technique can be learnt and used before the next one arrives. Lesson puzzles are kept apart from the daily ones, and any lesson can be revisited.