Puzzle Royale
How to play Akari
Light every square with bulbs
Also known as Light Up, Bijutsukan.
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Light every square
Solve it by lighting every white cell in the grid. The shading shows what your bulbs currently light, so dark squares are the ones still needing a beam.
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Tap to place a bulb
Tap a white cell once to drop a bulb, again to mark it "no bulb" as a note, once more to clear it. A bulb lights its whole row and column until a black wall blocks the beam.
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No bulb shines on another
Two bulbs may not sit in the same unbroken line of sight, and a numbered wall wants exactly that many bulbs in the cells directly beside it.
Play Akari now
Solving tips
- A 0 wall is a gift: none of its four neighbours can hold a bulb, so mark them all "no bulb" straight away.
- A wall whose number equals its free neighbours forces a bulb in each of them — fill those first.
- A cell no beam can ever reach must hold a bulb itself — hunt for cells boxed in by walls.
- When only one white cell in a beam-line can still light an unlit square, that cell is forced to a bulb.
- Every bulb you place lights a cross of cells — mark them lit in your head so you don’t waste a second bulb on them.
Where Akari comes from
- A Nikoli original called Bijutsukan — "art gallery" — where the bulbs are lights illuminating every corner of the room.
- Known in English as Light Up, and closely related to the classic "art gallery" illumination problems of computational geometry.
- Proved NP-complete in 2005 by Brandon McPhail — the same hardness verdict every family in this game shares.
- A bulb lights until a wall stops it, so the walls do double duty: they carry the number clues and they shape every beam.
- The numberless black walls are pure geometry — they never constrain a count, only block and channel the light.
Play it against a hundred other solvers
Puzzle Royale wraps Akari and seven other logic puzzles in a battle
royale: a hundred solvers enter, four rounds, half the field goes out each time,
one champion. Or play it untimed in Practice with no stakes at all.
Try a Akari puzzle
The other seven