Yajisan Kazusan Description
Yajisan Kazusan is a puzzle originally from nikoli; their description is only in Japanese, so for external links you may have to settle for Wikipedia’s very brief article. The object is to shade in some of the grid squares. No two shaded squares should be adjacent, and all of the unshaded squares should be in one contiguous region – equivalently, any two unshaded squares should have a path joining them through adjacent unshaded squares. Squares with a number and arrow are clues, and may also be shaded or unshaded. If a clue is unshaded, the number tells how many shaded squares the arrow points to. If a clue is shaded, it gives no information (it can be right or wrong).
Below is an example puzzle and its only solution.