(Japanese: 黒枡はどこだ？, Hepburn: Kuromasu wa doko da?
), abbreviated Kuromasu (黒マス) or Kurodoko (黒どこ), is a binary-determination logic puzzle published by Nikoli.
A book consisting entirely of Kuromasu puzzles has been published by Nikoli.
The following rules determine which cells are which: A number of methods of solving Kuromasu puzzles exist.
The English language Nikoli website uses Engrish to translate the name as "Where is Black Cells".