Sukaku
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Tap a number to eliminate it from selected cell
Progress0%
Easy · Sukaku
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How to play Sukaku
Every cell starts with a set of candidate digits shown as pencilmarks. Press a number to eliminate that candidate from the selected cell. When only one candidate remains, the digit is placed automatically. Cells showing a single large digit are fixed and cannot be modified. Standard Sudoku row, column, and box rules apply.
Full guide →
A pencilmark-style variant where clues are given as candidate sets
What is Sukaku?
Sukaku (数角) is a Sudoku variant where instead of given digits, each cell is given a set of possible candidates. The solver must eliminate candidates using standard Sudoku logic until each cell has exactly one remaining candidate. Some Sukaku puzzles provide very sparse candidate sets (near-complete givens), while others provide full or nearly-full candidate lists, requiring advanced techniques to solve.
At a Glance
| Constraint type | Pencilmark Elimination |
| Typical givens | All candidates shown |
| Difficulty rating | ★★★☆☆ 3/5 |
| Avg. solve time — Easy | 8 min |
| Avg. solve time — Medium | 18 min |
| Avg. solve time — Hard | 35 min |
| Avg. solve time — Expert | 62 min |
How to Solve Sukaku
| Technique | What it does | Level |
|---|---|---|
| Candidate Scanning | Start by scanning rows, columns, and boxes — any candidate appearing in only one cell in a group must be placed there. | Beginner |
| Cross-Hatch Elimination | When a digit is placed (or reduced to one candidate), eliminate it from all cells in the same row, column, and box. | Beginner |
| Naked Singles | A cell with only one remaining candidate is a naked single — the digit is forced. In Sukaku, this happens automatically when you eliminate down to one candidate. | Intermediate |
| Hidden Singles | A candidate that appears exactly once in a row, column, or box must be placed in that cell regardless of how many other candidates that cell shows. | Intermediate |
| Pair Elimination | Two cells in a group that share only the same two candidates form a naked pair — both candidates can be eliminated from all other cells in that group. | Advanced |
Average Solve Times
Easy
8 min
Medium
18 min
Hard
35 min
Expert
62 min
Frequently Asked Questions
What is Sukaku?
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.
How is Sukaku different from regular Sudoku?
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.
Are the starting pencilmarks always correct?
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.
What techniques work best in Sukaku?
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.
Is Sukaku harder than regular Sudoku?
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.
How long does Sukaku take to solve?
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.