How to Solve Akari (Light Up): A Strategy Guide

Updated June 2026

Akari — also known as Light Up — asks you to place light bulbs on a grid so the whole board is illuminated. It looks open-ended at first, but the numbered walls and a single sharp restriction (no bulb may shine on another) combine to force most placements. Here is how to read those clues and light the board with logic instead of trial and error.

The rules

• Place bulbs in white cells. A bulb sends light along its row and column in all four directions until the light hits a black wall or the edge of the grid.
• Light every white cell. When you are done, no white cell may be left dark.
• No bulb shines on another bulb. Two bulbs can never sit in the same row or column with nothing but white cells between them — each would light the other.
• Numbered walls are exact. A number on a black cell tells you precisely how many bulbs are orthogonally adjacent to it (up, down, left, right) — no more, no fewer.

Start with the extreme clues

The numbered walls are your opening. A 0 means none of its four neighbours hold a bulb — mark all of them as "no bulb" immediately, which removes options and often forces a nearby cell to be lit a particular way. A 4 is the opposite: all four neighbours must be bulbs, so place them at once. A 3 in the middle of the board has four neighbours and needs three bulbs; the moment one neighbour is ruled out (by an edge, another wall, or a no-bulb mark), the remaining three are forced. Always sweep the high and low numbers before anything else.

Count the room a number has

Every numbered wall is a little counting puzzle. Compare its value to the number of neighbours that could still hold a bulb. If a "2" has exactly two viable neighbours left, both are bulbs. If a "1" already has one bulb beside it, its other neighbours become no-bulb cells. This is the same accounting you use in Minesweeper, and it cascades the same way: each forced bulb or no-bulb mark tightens the walls around it.

Find cells with only one way to be lit

Switch perspective from "where can a bulb go" to "how can this cell get lit". Look at a dark white cell and trace the directions light could reach it from. If walls and edges leave only a single cell from which a bulb could illuminate it, that cell must hold a bulb — there is no other source of light. White cells boxed in on several sides by walls are the easiest place to find these forced bulbs, and a corner pocket with one opening practically hands you the answer.

Use the no-two-bulbs rule to eliminate

The restriction that bulbs cannot see each other is not just a constraint to obey at the end — it is a tool for ruling cells out as you go. The instant you place a bulb, every white cell it lights along its row and column is now a no-bulb cell, because a second bulb there would face the first. Mark that whole line of light. Those marks frequently leave a numbered wall with just enough room to force its remaining bulbs, or leave a dark cell with a single possible light source.

Watch for cells that force a bulb on themselves

Sometimes a white cell can be lit by no other cell at all — every line into it is blocked by walls except the cell itself. Then the cell must contain a bulb, because nothing else can ever illuminate it. Scanning for these self-lighting cells, especially in tight corridors between walls, breaks open boards that look stuck.

A reliable order of attack

1. Resolve every 0 (mark no-bulb) and every 4 and 3 you can (place bulbs).
2. For each remaining number, compare its value to its free neighbours and place or eliminate.
3. After every bulb, mark its entire line of light as no-bulb.
4. Hunt for dark cells with only one possible light source and place those bulbs.
5. Loop until every cell is lit and every number is satisfied.

A proper Akari has one unique solution reachable by deduction, so you never have to gamble — there is always a wall whose count forces a move or a dark cell with a single source. When the last cell lights up and every number checks out, you are done.