Published at Monday November 15, 2021
Random generation of Sudoku-X usually produces a lot of extremely difficult puzzles. So I generated a lot and uploaded the ones which required only solving techniques like Naked and Hidden Subsets, Connected Pairs (a.k.a. Crossover), Basic Fish, Remote Pairs, BUG, Skyscraper, 2-String Kite, up to XY-Wing. You can find them for at least 10 years into the future at my X-File page.