Kuromasu

Kuromasu (also known as Kurodoko) is a logic puzzle published by Nikoli. The name "Kuromasu" is Japanese for "black cells."

The puzzle is played on a rectangular grid. Some cells in the grid contain numbers. The objective is to determine which of the remaining cells should be painted black, based on the following rules:

• Rule 1: Numbered cells cannot be painted black. The number in a cell represents the count of white cells (including the numbered cell itself) that can be seen from that cell horizontally and vertically until blocked by a black cell or the edge of the grid.

• Rule 2: No two black cells can be horizontally or vertically adjacent. Black cells can be diagonally adjacent.

• Rule 3: All white cells must be connected horizontally or vertically. That is, it must be possible to move from any white cell to any other white cell without moving through any black cells.