How to find your next move in Akari

Two 4s share a square on this board. Filling them gives you seven bulbs, the position shown on our home page. The next move comes from counting the bulbs already touching a 3. Follow along in this exact board in Simon Tatham’s Light Up.

Columns run from A to G. Row 1 is at the top. A dot is an open square, # is a wall, and a digit is a numbered wall.

    A B C D E F G
1   . . . . . . .
2   . # . # . 3 .
3   . . 4 . # . .
4   . 3 . # . # .
5   . . 4 . # . .
6   . 2 . 2 . 2 .
7   . . . . . . .

Start with the two 4s

Place bulbs above, below, left and right of C3. Do the same around C5. Count C4 only once. Its bulb touches both clues. The seven bulbs are at C2, B3, D3, C4, B5, D5 and C6.

What can you mark next?

Look at the 3 on B4. B3, C4 and B5 already hold bulbs. A fourth bulb at A4 would touch the same clue, so mark A4. A mark means you have ruled out a bulb there. It can still receive light.

• The 2 on B6 already touches bulbs at B5 and C6. Mark its two remaining neighbors, A6 and B7.
• The 2 on D6 already touches bulbs at D5 and C6. Mark E6 and D7.

Where can the light for E6 come from?

E6 needs light and you just ruled out putting a bulb there. D6, F6 and E5 are walls. That leaves a single open neighbor below it. Put a bulb at E7. Its beam travels up to E6 and across the whole bottom row, passing through your marks at B7 and D7.

Here is a second way to force a bulb. E4 is surrounded by four walls. No beam can enter, so E4 needs its own bulb.