Gyokuseki ("Gyokusekikonko Puresu"; from Japanese, literally "gems and stones") is a logic puzzle created by Naoki Inaba (Japan). The aim is to fill a square grid with black circles ("gems") and white circles ("stones"). Every row and every column contains one black circle and random quantity of white circles. A number at the edge of the puzzle indicates how many circles can be seen in the corresponding row or column up to and including the black circle.
Cross+A can solve puzzles from