Light Up is a single player game played on a rectangular grid. Initially, the cells of the grid are either white or black, where black cells can optionally be labeled with an integer between $0$ and $4$ (inclusive).
The player can place light bulbs into white cells. Specifically, a light bulb $b$ lights a white cell $c$ if $b$ lies on the same row or column as $c$ (or both, i.e., $b$ is placed on $c$) and the portion of the row/column between by $b$ and $c$ contains no black cells. The goal is to find an arrangement of light bulbs such that:
The figure shows an instance of Light Up (left) and a possible solution (right).
The problem of deciding whether an instance of Light Up admits a solution is NP-Complete .
 B. McPhail, “Light Up is NP-complete”.