Nurikabe (taken from Nikoli)
- Fill in the cells with black under the following rules.
- You cannot fill in cells containing numbers.
- A number tells the number of continuous (adjacently) white cells. Each area of white cells contains exactly one number in it and they are separated by black cells.
- The black cells are linked to be a continuous (adjacently) wall.
- Black cells cannot be linked to be 2x2 square or larger.
This seems to be a correct solution: