Kuromasu (from Japanese "kuromasu wa doko da", literally "Where is black cells?"; also known as "Kurodoko") is played on a rectangular grid. Some of these cells have numbers in them. Each cell may be either black or white. The object is to determine what type each cell is.
The following rules determine which cells are which:
- Each number on the board represents the number of white cells that can be seen from that cell, including itself. A cell can be seen from another cell if they are in the same row or column, and there are no black cells between them in that row or column.
- Numbered cells may not be black.
- No two black cells may be horizontally or vertically adjacent.
- All the white cells must be connected horizontally or vertically.
Cross+A can solve puzzles from 3 x 3 to 30 x 30.