Author: Vladimir Portugalov
Fill some cells with stars so that 3 stars appear in every row and column. Each bold-outlined area should contain exactly one star. Cells with stars cannot touch each other, not even diagonally.
Grid control: Click the mouse button at the selected cell to set/remove a star. Second click will put auxiliary cross sign, which doesn't affect correctness of the solution, but helps visually. You can also drag the content of one cell to another with the mouse. More details about grid control are at the help page.