Rules: Place lightbulbs in some of the cells such that the whole grid is lit (that is, each blank cell is lit by at least one lightbulb). A lightbulb lights a blank cell if it’s on the same row or column, and there’s no walls (black cells) between the cell and the lightbulb. Lightbulbs may not light other lightbulbs: if two lightbulbs are on the same row or column, there must be a wall between them. A clue tells how many lightbulbs there are in the four surrounding cells.
This puzzle type was invented by Nikoli.