How to play Akari

Akari, also called Light Up, is a logic puzzle played on a grid of open cells and walls. You place bulbs in open cells until the whole grid is illuminated.

The rules

1. A bulb lights its own cell and every open cell it can see horizontally and vertically.
2. Walls stop the light. Bulbs do not shine diagonally.
3. Two bulbs may not see one another.
4. A number on a wall is the exact number of bulbs in the cells immediately above, below, left, and right of that wall.
5. Every open cell must be lit when the puzzle is finished.

An unnumbered wall only blocks light; it does not restrict how many bulbs may touch it.

Your first deductions

A wall marked 0 forbids bulbs in every adjacent open cell, so mark those cells ×. At the other extreme, if a numbered wall still needs as many bulbs as it has available neighbours, every one of those neighbours must contain a bulb. For example, a 3 with exactly three usable adjacent cells fills all three.

Whenever you place a bulb, mark every visible cell in its row and column as unable to hold another bulb. Those cells are lit, but they are not necessarily finished: an unlit cell elsewhere may still require a bulb whose light passes through them.

A reliable solving routine

1. Resolve 0 walls and forced numbered walls.
2. Mark every cell seen by a confirmed bulb with ×.
3. Find unlit cells that can be illuminated from only one possible position.
4. Recount each numbered wall after every new bulb or ×.
5. Repeat until all open cells are lit and every number is exact.

Controls on this site

Tap or click an open cell to cycle bulb → × → empty. The × is a note that a bulb cannot go there; light can still pass through it. Your unfinished board is saved automatically in this browser.

Ready to illuminate a district? Play Light the City, or learn the Akari solving techniques used on larger grids.