In akari, the grid must be filled with light bulbs so that every square is illuminated. When a light bulb is placed in the grid, it illuminates every square in a horizontal or vertical line that isn’t blocked by a black square. However, no light bulb may be illuminated by another light bulb, and the bulbs must be placed so that each numbered black square has the correct number of light bulbs adjacent to it. The rules are simple to remember, but create a complex logical world that sudoku solvers will truly appreciate.