A free app for Android, by Wetpalm.

Kuromasu (Black Is Always Right) is a logic puzzle game where the objective is to find the black cells. This is a puzzle game where the rules are simple, yet very challenging. This game can be fun and addictive, especially if you like Sudoku, Shikaku, or Kakuro.

The rules are simple: You have to fill the grid with numbers from 1 to 9, with one exception. You can only use the numbers that are in the grid, so it is impossible to use 1 or 9 in the same row, column, or box.

Kuromasu can be challenging, especially if you are a beginner. If you are a beginner, it is recommended to start with a small puzzle size.