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Sukaku is a Sudoku variant where every cell in the 9×9 grid starts pre-filled with a set of pencilmark candidates instead of given digits. Your task is to eliminate incorrect candidates using standard Sudoku rules until exactly one digit remains in each cell. All 81 cells begin with multiple possibilities.

In classic Sudoku, some cells are pre-filled with confirmed digits. In Sukaku, no cell has a confirmed digit — instead, each cell shows a subset of possible digits as pencilmarks. The starting pencilmarks are curated by the puzzle constructor and are always consistent with the unique solution.

Yes. The pencilmarks shown at the start of a Sukaku puzzle represent a valid subset of candidates for each cell — they are never wrong, but they may include more candidates than strictly necessary. Your job is to eliminate all but the correct digit using logical deductions.

All standard Sudoku elimination techniques apply: naked singles (when only one candidate remains in a cell), hidden singles (when a digit can only go in one cell within a row, column, or box), naked pairs, pointing pairs, and advanced techniques like X-Wings and Swordfish. The absence of given digits means you rely entirely on elimination.

Easy Sukaku is more forgiving than classic Sudoku because the pencilmarks are already provided — you never have to work out candidates from scratch. Hard and expert Sukaku puzzles with minimal starting candidates require the same advanced techniques as difficult classic Sudoku.

Easy puzzles take 5–15 minutes. Medium puzzles run 15–30 minutes. Hard puzzles average 30–60 minutes and expert puzzles can take over 90 minutes. Solve time scales with how many eliminations each technique step provides.