How to play Akari
Akari (Light Up) hands you a dark grid and a box of bulbs. The wall numbers and the no-shine rule pin down every placement — here's how to read them.
The rules
- Place bulbs on white cells. A bulb lights its row and column until a wall blocks the beam.
- Every white cell must end up lit.
- No bulb may be lit by another bulb — bulbs never see each other.
- A numbered wall (0–4) must touch exactly that many bulbs, counting only the four orthogonal neighbors.
- Unnumbered walls are just obstacles.
Controls
- Tap an empty cell → 💡 bulb. Tap again → · dot ("no bulb here"). A third tap clears.
- Lit cells tint amber so you always see your coverage; the counter tracks lit cells.
- Rule-breaking bulbs and impossible numbers outline in red if you pause.
Solving strategies
- Zeros first. A 0 wall means no bulbs on any side — dot all its neighbors. Those dots often squeeze nearby numbers.
- Full-count walls. If a number equals its free neighbors (a 4, a 3 on an edge, a 2 in a corner), all of them are bulbs.
- Satisfied walls dot the rest. Once a number has its bulbs, dot its other neighbors.
- The lonely-cell rule. Take an unlit cell and list every place a bulb could light it from (including itself). If only one candidate remains, it's a bulb. This is the deduction that finishes most boards.
- Diagonal squeeze. Two diagonal 1-walls sharing two candidate cells can't both use the shared pair — the outer cells get dots. Rare but elegant.
A worked example
A "3" sits against the top edge, so it has at most three free neighbors — all three are bulbs immediately. Each new bulb beams light down its column, dotting every cell it sees. A neighboring "1" that now touches one of those bulbs is satisfied, so its remaining neighbors get dots too. One of those dotted cells was the last candidate for lighting a far corner cell — so that corner cell must hold its own bulb. Three rules, four placements, and the whole region is done.
Common mistakes
- Placing bulbs in sight of each other. Check the full row and column before you tap — beams travel until a wall, however far that is.
- Treating numbers as minimums. They're exact: a 1 with two adjacent bulbs is broken.
- Skipping the dots. Dots are how deductions chain. If you only place bulbs, the lonely-cell rule is invisible.
- Forgetting diagonals don't count. Wall numbers only look up, down, left and right.
Frequently asked questions
- What does "Akari" mean?
- "Light" in Japanese — the puzzle is also known as Light Up and first appeared in Japanese puzzle magazines.
- Do I ever need to guess?
- No — every board here is generated to be solvable by pure step-by-step logic with exactly one solution.
- Is there a daily puzzle?
- Yes — a shared 10×10 Daily Challenge with streaks, plus unlimited boards in 7×7 and 10×10. Free, no login.