Kurodoku
Shade cells using visibility numbers
Kurodoku is a cell-shading logic puzzle where numbered cells indicate visibility — how many white cells can be seen looking in all four directions from that cell (including itself). You shade some cells black, but white cells must remain connected, and no two black cells can be orthogonally adjacent. The interplay between visibility constraints, connectivity, and the no-adjacent-black rule creates deeply satisfying logical deductions.
How to Play Kurodoku
Visibility Numbers
A number in a cell tells you how many white cells are visible from that position looking up, down, left, and right (including itself). Black cells block sight.
Shade Cells
Mark some cells as black. The remaining white cells must satisfy all visibility numbers.
White Connectivity
All white cells must form one connected group. You can reach any white cell from any other through orthogonal white-cell moves.
No Adjacent Black
No two black cells can share an edge (be horizontally or vertically adjacent). They can be diagonal to each other.
Numbered Cells Stay White
Cells with numbers are always white. They can never be shaded black.
Complete Deduction
Every cell must be determined as black or white through logical deduction. No guessing needed.
Strategy & Solving Tips
Expert Kurodoku solving combines visibility counting with connectivity analysis and the no-adjacent constraint.
- A cell with visibility equal to its maximum possible (seeing all the way to walls in every direction) means no cells in its sight lines can be black
- Low visibility numbers near the center of the grid indicate nearby black cells blocking the view
- If shading a cell would disconnect white cells, it must stay white
- The no-adjacent-black rule means every black cell has a white buffer around it on all four sides
- Check visibility after each black cell placement — if any numbered cell's count becomes impossible, undo that placement
- Cells between two numbered cells with constrained visibility can often be determined as definitely white or black
Kurodoku FAQ
Do visibility numbers count the cell itself?
Yes. A numbered cell counts itself in its visibility total. So a cell showing "1" can see only itself — all four orthogonal neighbors must be black (or walls).
Can a numbered cell see through other numbered cells?
Yes. Visibility is blocked only by black cells and grid edges. White cells (including other numbered cells) do not block sight.
What if all cells around a numbered cell must be white?
This happens when the visibility number requires seeing far in multiple directions. Follow the deduction and ensure no black cells are placed in those sight lines.
Is Kurodoku related to other puzzles?
Kurodoku shares elements with several puzzle types: visibility counting similar to Skyscrapers, cell shading like Nurikabe, and connectivity requirements found in many Japanese logic puzzles.
Ready to Play Kurodoku?
Test your visibility reasoning with Kurodoku — where every number tells a story about what it can see, and every shaded cell changes the entire picture.