The "Grid" on the left above is a typical sudoku problem. It is divided into "Columns" and "Rows" that are labelled in our demonstration. The Grid contains a total of 81 "Cells"
Each Cell can be referenced by the Column name and the Row name. In the above Grid the red Cell is reference F6 (Column F and row 6)
In addition, there are 9 "Boxes" each containing 9 Cells as shown on the right above. In this demonstration we have shaded the different "Boxes" so that you can easily see which is which but you will not usually find this in Sudokus
Each Sudoku has a unique solution that can be reached logically without guessing. You need to enter digits from 1 to 9 into the blank cells so that every row, every column and every "Box" contains the numbers 1 to 9 inclusive
Each time that you press "Next" a new number (shaded red) will be inserted into the grid and the explanations tell you why the new number can only be the number shown