The "Light Up" puzzle (also known as "Akari", "LightUP" and "lanterns") is a rectangular box in which some cells are white, and some are black. The black cells can contain numbers from 0 to 4. The goal of the puzzle is to place light bulbs in empty cells so that all white cells are illuminated.
The light from the bulb is distributed in a straight line horizontally and vertically until you hit a black cell or the border of the field. Bulbs should not face each other. If there is a number in a black cell, then it must be adjacent (on the left, top, right or bottom) to a specified number of bulbs, no more and no less.