This is an example of a completed Region Sum Line Sudoku Puzzle.

Each lines passes through multiple regions, the total of the cells in each region must be the same.

If you follow the line that start in the top-left region, you can see the same total for each region,

1. 2 + 5 + 8 = 15
2. 8 + 2 + 5 = 15
3. 4 + 2 + 9 = 15
4. 2 + 4 + 9 = 15

If a line passes through the same region twice (or more), it counts as 2 separate regions - there is an example of this in the bottom-left.

The usual rules of Sudoku as well.