Published by Nikoli, Kurotto is an exquisite study in island areas and contiguous clusters.

Rules of Kurotto

• Circle Sanctuary: Cells containing circles can never be shaded.
• Neighborhood Sum: Each circle's number represents the exact sum of cells in all shaded connected components that touch that circle orthogonally.
• Component Identity: If a black polyomino wraps around a circle and touches it at both top and left, all of its cells are counted only once.
• Nikoli Contact Law: Every black group must be tethered to at least one circle. You can never create an isolated black cell in the corner with no path to a clue.

Solving Techniques

Look immediately for 0 circles: all four of their orthogonal neighbors must be unshaded (use Dot mode to lock them in). If a 1 circle has only one open unshaded neighbor, that neighbor must be black and must not expand any further! For larger numbers like 5 or 6, look at the narrow channels between clues to see if two clues can share a single black bridge.