An AKARI or Light Up puzzle consists of a square grid in which some of the cells are blocked out in the same way as in a crossword puzzle. Think of it as the floor plan of a building in which the blocked out cells represent pillars or wall segments. The remainder of the cells represent floor area which must be illuminated by lamps placed in certain of the cells. A lamp illuminates all cells in its row and column up to the edge of the puzzle, or up to an intervening blocked out cell. No lamp is allowed to illuminate any other lamp, and the numbers in some of the blocked out cells indicate the number of lamps which are adjacent to that cell both horizontally and vertically. Each puzzle has a unique solution which does not require any guessing to achieve.
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