This is subtraction sudoku.
The rules are basically the same as common Sudoku, but with a few additions.
In the row, the number in the orange box is the difference when its left side (sum of 3 squares) is subtracted from its right side (sum of 3 squares). Similarly, for columns, the number in the box is the difference between its top side and its bottom side.
There is only 1 unique solution! Find it!