Place light bulbs in selected white cells so that each white cell is illuminated. Light bulbs illuminate every white cell in all four orthogonal directions until blocked by a black cell. No light bulb can be illuminated by another light bulb. Clue numbers correspond to the number of light bulbs in the four orthogonally adjacent cells.

Example puzzle

Grid control: Click the mouse button at the selected cell to set/remove a bulb. Second click will put auxiliary cross sign, which doesn't affect correctness of the solution, but helps visually You also can draw a line to mark illuminated cells. More details about grid control are at the help page.