Akari 美術館 (Bijutsukan)

Play on a grid of white and black cells. Place bulbs in white cells only. Each bulb lights its row and column orthogonally until blocked by a black cell or the grid edge. No two bulbs may illuminate each other—i.e. no two bulbs in the same row or column with only white cells between them. Black cells show 0–4: that is exactly how many bulbs must be orthogonally adjacent (not diagonal). Unnumbered black cells allow any number. Solve by logic; unique solution. Strategies: cells adjacent to 0 can never have bulbs—mark them safe. Cells adjacent to 4 must all have bulbs. Work inward from corners and edges where options are fewest.

Akari first appeared in Nikoli in 2001. In Japan it is Bijutsukan (art gallery)—black cells are walls, bulbs light the halls. The English name "Light Up" and "Akari" (light) are used internationally. Nikoli's language-free pencil puzzles spread from Japanese magazines to global print and digital platforms. Puzzle cafes in Tokyo stock Nikoli collections.

Start with all 0-cells: mark every neighbouring cell as "no bulb." Then process 4-cells: place bulbs in all four adjacent cells. A white cell that can only be lit by one possible bulb position must have that bulb. Work inward from corners and edges where the grid geometry limits options. If placing a bulb would leave another cell unlit and unreachable, that bulb position is wrong.

Nikoli pencil puzzle tradition; language-free design enables global publication. Print magazines in Japan; digital worldwide. Puzzle cafes in Tokyo feature Nikoli collections. Akari (Light Up) is known as Bijutsukan in Japan—black cells are gallery walls, bulbs light the halls. The puzzle rewards deductive logic; no guessing required. Available on Nikoli.com, Conceptis Puzzles, and Simon Tatham's Portable Puzzle Collection.

Play free at Nikoli.com (official Nikoli site), Conceptis Puzzles (conceptispuzzles.com—search "Light Up"), and Simon Tatham's Portable Puzzle Collection (chiark.greenend.org.uk/~sgtatham/puzzles). Mobile apps include Conceptis Light Up and various Nikoli puzzle collections.