This is a new puzzle variant that combines numberlink and sudoku.
1. Normal Sudoku rules apply - each column, row, and 3x3 box must contain all of the digits 1 through 9.
2. There is an anti-knight restriction. This means that all cells which are a chess knight's move apart may not contain the same digit.
3. The numbers on the arrows indicate the sum of the digits to be placed along their respective pointed diagonals. The value of "X" must be determined.
4. The grid provided represents a numberlink puzzle in which all of the numbers (one pair of each digit, 1 through 9) have been replaced by empty circles. Each pair of matching numbers must be connected via an orthogonal path ("link") that does not intersect any other link.
5. The digit on a link's endpoints must not exist in any other cells on that link's path.
6. Every cell must be used by precisely
one link - not zero, and not more than one.
7. No link may touch itself. In other words: for each link, there is no orthogonal path between the endpoints that uses some, but not all cells on the link
Here is an example image which shows a path with 8 on the endpoints. Cells highlighted in red may not contain 8 because of rule #5. The other undetermined endpoints may not contain an 8 due to rule #4 (all endpoint pairs must be differently numbered). The orange cells can be ruled out by normal sudoku rules. All of these rules combine so that 8 in the 3x3 box must appear in the center cell.
Here is an example of an illegal numberlink path (see rule #7).
Penpa link to play