This Kropki Sudoku puzzle consists of a 9x9 grid with the addition of either open or closed circular markers between neighbouring pairs of squares.
Closed circles show all adjacent pairs of squares where the value in one square is double the other, while open circles show all pairs where one value is consecutive to the other.
'Consecutive' means that the numbers in the two squares have a numerical difference of '1'. For example: 2 and 3 are consecutive, as are 6 and 5.
To solve Kropki Sudoku you must place 1 to 9 once each into every row and column while also obeying the circular markers.
It's important to note is that all circular markers are given, so if there is no marker between two squares then they are not consecutive and one is not double the other.
When 1 and 2 are in adjacent squares then either an open circle or a closed circle will be given (since both are true).