Hard Sudoku: stay systematic when progress slows
Hard boards are intended for patient candidate work. In Voku, the label has a precise limit: the documented basic evaluator stopped with cells unresolved. It does not claim one specific advanced technique or make guessing acceptable.
Who this level is for
Experienced players who can maintain full candidate notes, verify eliminations, and back away from an unsupported assumption.
What to expect
Long quiet stretches, subtle interactions, and more need to revisit earlier units. Hints remain available, but using one is recorded in the local result so you can measure your own progress honestly.
How Voku defines this level
The current evaluator applies naked singles, hidden singles, locked candidates, naked pairs, and hidden pairs. If those modeled steps cannot finish the unique-solution board, it is labeled Hard. Human solvers may find another valid logical route.
A reliable approach
- 01Refresh all candidates before looking for a complex pattern.
- 02Compare the same digit across neighboring boxes and lines.
- 03Separate confirmed logic from trial assumptions.
- 04Pause deliberately; the timer pauses only when you choose Pause.
Techniques worth practicing
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