Akari (Light Up)Free, no sign-up

(1) Place bulbs on white cells. (2) A bulb lights its row and column until the light hits a black cell or the edge of the board. (3) No two bulbs may light each other (in the same row or column with no black cell between them). (4) A numbered black cell shows how many bulbs are directly above, below, left and right of it. (5) The puzzle is solved when every white cell is lit.

Yes. Bijutsukan ("art gallery") is the name used by the Japanese puzzle magazine Nikoli, and the puzzle is widely known as Light Up or Akari. The rules are identical.

Each tap on a white cell cycles bulb → dot (·) → empty. A dot is a note meaning "no bulb here" and does not affect the solution. Right-click toggles just the dot. On a keyboard, choose a cell with the arrow keys and press Space or Enter to cycle it.

Yes. Every puzzle is built to have a unique solution. You can solve it with logic alone, such as "a 4 is surrounded by bulbs on all sides", "no bulbs next to a 0", or "a cell that only one spot can still light".

By the time from opening the puzzle to solving it, fastest first. You only need a nickname, and you can submit up to 30 times a day per size. The server checks that your board follows the rules.