Kuromasu (Kurodoko)
Where are the black cells hiding? Deduce shadows from orthogonal line-of-sight clues while keeping all white squares seamlessly connected!
Kuromasu Rules & Objective
Published by Nikoli, Kuromasu (“Where is Black Cells?”) is one of Japan's most enduring binary spatial puzzles:
Master Deductive Tactics
1. The White Cushion Rule
As soon as you find a black cell, immediately place white markers on its North, South, East, and West neighbors. This single rule triggers chain reactions across the entire grid!
2. Distant Blockers for Small Clues
If a clue is 2, it can see only one neighbor beyond itself. Any cell situated 2 or more steps away in any direction must be blocked by a black square to prevent the sightline from expanding too far.
3. Large Clue Expansion
If a clue has a large value near the theoretical maximum of its row and column, nearly all squares along its rays must remain white. Any cell whose shading would truncate the clue below its required value must be white.
4. White Connectivity Traps
Never place a black square if doing so leaves a corner white cell or a dead-end corridor with zero orthogonal exits to the rest of the board. All white cells must breathe into one continuous body.
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