This year, we started posting some extra difficult Sunday Stumpers, about once a month. These will be quite tough puzzles, but with a logical path to be found (and solution videos to help). This eleventh Sunday Stumper is a challenging (anti-)XV Sudoku by Murat Can Tonta.
or solve online (using our beta test of Penpa-Edit tools)
Author/Opus: This is the 214th puzzle from our contributing puzzlemaster Murat Can Tonta.
Rules: Standard Sudoku rules. Also, whenever the numbers in two adjacent cells sum to exactly 10 or 5, an X or V is placed on the edge between cells reflecting the Roman numerals for 10 or 5. All adjacent cells not marked with an X or V cannot add up to 10 or 5.
Difficulty: 5 stars
Time Standards (highlight to view): Grandmaster = 17:30, Master = 30:00, Expert = 1:00:00