Invented by Nikoli, Yajisan-Kazusan introduces a brilliant philosophical twist to grid puzzles: clues themselves can be deceptive if they reside inside shaded cells!

Core Axioms

• No Consecutive Blacks: If cell \((r, c)\) is shaded black, all four of its orthogonal neighbors must be unshaded (white).
• White Archipelago Unity: The unshaded white cells must never be cut into two or more isolated sections. A wall of black cells cannot span edge-to-edge.
• The Paradox of Shading: If treating a clue as true leads to a contradiction (e.g., forcing two black cells to touch or partitioning the white sea), that clue cell must be shaded black!
• Corner & Wall Trapping: Shading a corner cell or edge cell requires careful consideration of the adjacent cells so the white territory remains completely traversable.

Beginner Strategy Tips

Start by identifying clues pointing towards zero-capacity boundaries. If a 0-arrow points towards a wall of length 1 with a known black neighbor, test whether shading or unshading resolves the local neighborhood. Use the Dot mode to lock in verified white cells so your pathing remains crystal clear.