Sukaku
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
How do I place a digit in Sukaku?
You eliminate wrong candidates by pressing the number buttons. When only one candidate remains, the digit is placed automatically.
Can I accidentally eliminate the correct digit?
Yes — if you eliminate the solution digit, it counts as a mistake. The candidate is still removed from the cell.