Light Up (Akari) Strategy: Tips and Solving Techniques

1. Count the four touching cells, not the beam

Every number sits on a black wall and counts the lamps in the cells touching it from above, below, left and right. A lamp further along the same row never counts, and diagonal neighbours are ignored.

That is the rule that wastes games: a lamp's beam travels until a wall stops it, but its count lasts one square. A wall marked 2 wants exactly two lamps among its four touching cells.

• A wall marked 4 needs lamps in all four touching cells, so fill the ring the moment one appears.
• Walls whose neighbour cells overlap share that gap, so one lamp can satisfy two numbers; recheck both after every placement.

2. Zero walls are the cheapest forced moves

A wall marked 0 expects no lamps beside it, so none of the four cells around it may hold one. That instantly blocks those cells and usually settles the first moves of the board.

Blocked cells still must end up lit, though. Each one needs a lamp further along its row or column; the zero only forbids a lamp living right next to the wall.

3. Keep a running tally on every numbered wall

Light Up is bookkeeping. Once a wall's number is met, its still-empty neighbours can never take a lamp, yet they still need light from elsewhere.

The mirror move is just as common: when a wall still needs lamps and its free, legal neighbours number exactly that need, every one of them must be a lamp. Place them all at once.

• A wall needing two lamps whose only free neighbours sit on opposite sides pins both squares immediately.

4. No corridor can hold two lamps

A lamp shines until the first wall in each direction, so two lamps in the same unbroken row or column stretch beam straight into each other. That facing pair is illegal, and the game rings both cells red.

Think of walls as carving the board into corridors, each a maximal run of empty cells between walls or between a wall and the board edge. A corridor holds at most one lamp, so once it has one, no other cell along it can take a lamp.

• An unlit cell in a corridor whose lamp is already placed can only be saved by a lamp arriving from a perpendicular corridor.

5. Pockets, edges and forced lamps

Hunt for cells the board has trapped. If every orthogonal neighbour of an empty cell is a wall or the board edge, no outside beam can reach it, so the cell itself must hold the lamp.

Softer pockets behave the same: a cell wedged against walls and edges often has just one corridor that can light it. When walls or clue constraints rule out every cell of that corridor, the pocket itself takes the lamp.

• A corner wall still needing two lamps with free neighbours on opposite sides settles both squares at once.

6. Let dark cells point at the next lamp

Unlit squares render darker than lit ones, so the board shows exactly where work remains: every dark cell must gain a beam from a lamp in its row corridor or column corridor.

Pick a dark cell and list its possible light sources among those corridors, excluding blocked cells, cells already facing a lamp, and cells that would over-fill a wall. Exactly one candidate means place it; none means an earlier lamp is wrong.

• Rerun the check after every lamp; lighting one cell often makes its neighbour the new bottleneck.

7. A steady order of attack

Warm up on Easy (7×7), where a few numbered walls teach the rhythm, before Hard's 10×10 boards cut the clues and thicken the walls so missed moves compound fast.

Placement order matters less than rechecking: after each lamp, scan nearby walls for satisfied counts, watch the red highlights, and confirm no unlit pocket was sealed off. The Hint button places one correct lamp or removes a wrong one when the chain stalls.

• Daily Light Up shares one medium board with all players, so rehearse the 10×10 grid in free play before racing the clock.