How to Play Sudoku
Sudoku is a classic logic puzzle where the goal is to fill the grid with digits such that there are no duplicates in any row, column or subgrid.
Rules
- The board is divided into cells and subgrids.
- Each cell gets a numeric value 1, 2, 3... (for a 4×4, numbers 1–4)
- Numbers cannot repeat in any row or column.
- A 4x4 puzzle is also divided into four 2x2 subgrids. 9x9 puzzles are divided in nine 3x3 subgrids.
- Each subgrid may not have repeat digits.
- Circled values are called reveals and already show the correct value.
Basic strategies
- Look for columns and rows which have the fewest unknown values. In this case the last cell of column 1 must be a 4.
- Look for subgrids with the fewest number of unknown values. In this case the missing value in the first cage must be a 4 and the missing value in the second cage must be a 2.
- Look at the numbers which are most used in the grid. In this case there are three 4s known. There is only one position for the forth 4 without violating the unique column/row rule.
General Tips
- Use the notes feature to record candidate values in cells.
- Consider taking a hint if you get stuck.
- Re-scan after each placement.
See also: Calcudoku • Killer Sudoku