Standard between lines and anti-knight sudoku rules. That is:
1) Normal Sudoku rules apply.
2) Cells separated by a knight's move (in chess) cannot contain the same digit.
3) Digits along grey lines must be between the numbers in the two associated circles. Digits may repeat along between lines if allowed by other rules.
You can play it here: f-puzzles.
Solution code: Row 5 + Row 9 (18 Digits)
on 6. October 2021, 19:48 by ScatterBrain
So interesting the relationship of the 2 lines on top left sharing the same endpoints, and the 3 lines near row 6 and how they relate to each other.