Puzzle by Nikoli V Slitherlink

Nikoli Co., Ltd. (Japanese: 株式会社ニコリ, Hepburn: Kabushiki-gaisha; Nikori) is a Japanese publisher that specializes in games and, especially, logic puzzles. Nikoli is also the nickname of a quarterly magazine (whose full name is Puzzle Communication Nikoli) issued by the company in Tokyo. Nikoli was established in 1980, and became prominent worldwide with the popularity of Sudoku. The name "Nikoli" comes from the racehorse who won the Irish 2,000 Guineas in 1980; the founder of Nikoli, Maki Kaji, was fond of horseracing and betting. Nikoli is notable for its vast library of "culture independent" puzzles.