9x9 Sudoku puzzles, each with a unique solution, rated by the hardest human solving technique they require. Each puzzle is the one with the fewest clues that its difficulty level still solves, along a random clue-removal path. - "puzzle": The 9x9 grid as a list of rows, 0 for empty cells. - "solution": The solved 9x9 grid as a list of rows. - "difficulty": One of easy, medium, hard, extreme. The script used to generate this dataset can be found here.