Author: Vladimir Portugalov
Shade some empty cells black to create a single connected wall. No 2x2 square can be completely shaded. Numbers in a cell indicate the length of consecutive shaded blocks in the neighboring cells. If there is more than one number in a cell, then there must be at least one white (unshaded) cell between the black cell groups.
Grid control: Click the mouse button at the selected cell to change the filling of the cell. More details about grid control are at the help page.