You have a grid of squares. Some are filled in black; some of the black squares are numbered. Your aim is to ‘light up’ all the empty squares by placing light bulbs in some of them.
Each light bulb illuminates the square it is on, plus all squares in line with it horizontally or vertically unless a black square is blocking the way.
In order to win the game, you must satisfy the following conditions:
- All non-black squares are lit.
- No light is lit by another light.
- All numbered black squares have exactly that number of lights adjacent to them (in the four squares above, below, and to the side).
Non-numbered black squares may have any number of lights adjacent to them.