### Stostone

**Stostone** (*"Stone on Stone"*) is a logic puzzle invented by Nikoli. A rectangular or square grid is divided into regions. The goal is to blacken some cells of a grid ("stones") according to the following rules:

- All black cells in a region must be connected horizontally or vertically.
- A cell with a number indicates how many cells in the region must be blackened.
- In regions without a number any amount of cells may be blackened (at least one).
- When two cells are orthogonally adjacent across a region boundary, at least one cell must be white.
- If all stones "fall down", they must cover exactly the bottom half of the grid.

**Cross+A** can solve puzzles from **4 x 4** to **30 x 30**.