SUDOKU LEARNING CENTER
How to play Sudoku, from the basics to advanced variants
The goal is not to guess quickly. Find the only digit that satisfies every constraint. Use notes to track candidates and enter a number only when you have a clear logical reason.
A reliable Classic Sudoku workflow
- Scan every row, column and 3×3 box for missing digits.
- Add candidate notes to cells that are not yet determined.
- Look for a cell with one candidate or a digit with only one possible position in a region.
- Update your notes after every confirmed digit and repeat.
Techniques worth practising
A cell has only one possible candidate remaining.
A digit can appear in only one position within a region.
Candidates are confined to one row or column inside a box.
Two or three cells share the same candidate set, allowing eliminations elsewhere.
Rules for all eight variants
Every row, column and 3×3 box must contain 1–9 exactly once.
View details →Killer SudokuEach cage must reach its target sum without repeated digits while normal Sudoku rules still apply.
View details →Diagonal SudokuClassic rules apply, and digits cannot repeat on either long diagonal.
View details →Hyper SudokuClassic rules apply together with four highlighted Hyper regions.
View details →Anti-Knight SudokuClassic rules apply, plus equal digits are forbidden a knight's move apart.
View details →Odd–Even SudokuClassic rules apply together with each marked cell's parity.
View details →Thermo SudokuClassic rules apply and every thermometer must rise strictly.
View details →Arrow SudokuClassic rules apply, and every arrow sum must match its circle.
View details →Frequently asked questions
Which difficulty should a beginner choose?
Start with Easy or Medium to practise scanning rows, columns and boxes and to become comfortable with notes before attempting longer deduction chains.
When should I use notes?
Use notes when a cell still has two or more candidates. Remove candidates as soon as they are excluded by a row, column, box or variant rule.
Do hints invalidate an achievement?
Hints can teach the next logical step, but they are best used sparingly. Nova Sudoku records time and mistakes, so you can set a personal no-hint goal.
Is Puzzle IQ a real IQ score?
No. It is a playful in-game achievement label based on difficulty, not a psychological assessment or medical claim.