Kuromasu – Hard

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Kuromasu, also known as "Kurodoko," is a logic puzzle originating from Japan. It's played on a rectangular grid with some cells containing numbers. The main challenge is to determine whether each cell should be colored black or left white.

Basic Rules

1. The grid consists of cells that can either be colored black or left white.
2. Some cells already contain numbers, offering clues for solving.
3. The numbers in the cells indicate how many white cells, including the numbered cell itself, can be seen horizontally or vertically from that cell.
4. A cell is considered "seen" if it lies in the same row or column without any black cells obstructing the view.

Additional Rules

1. Cells containing numbers cannot be colored black.
2. Black cells cannot be adjacent, either horizontally or vertically.
3. All white cells must form a single connected group, meaning every white cell must be adjacent (horizontally or vertically) to another white cell.

Basic Solving Tips

1. Starting Point: Begin with cells having high numbers. They offer clues about long stretches of connected white cells.
2. Black Cell Blockers: If coloring a cell black obstructs the view of a numbered cell, preventing it from meeting its required count, then it must remain white.
3. White Cell Connectors: To ensure all white cells remain connected, look for cells that, if colored black, would isolate a group of white cells. Such cells must remain white.
4. Adjacency Rule: If a cell is determined to be white based on the above clues, any adjacent cells will be black, as no two black cells can touch.