Nikoli Classic • Light Up (Akari)
Light Up (Akari)
Place light bulbs to illuminate every corridor of the gallery. Respect wall clue counts and ensure no two bulbs beam directly at each other!
Illuminating gallery corridors...
Light Up (Akari) Rules
Published by the puzzle masters at Nikoli, Akari (meaning “light” in Japanese) is a pure deduction game of ray casting and space illumination:
1. Full IlluminationEvery single white corridor square must be lit by at least one lightbulb.
2. No Direct BeamsNo two bulbs may share an unobstructed horizontal or vertical line of sight.
3. Wall ConstraintsNumbered black squares require exactly that many bulbs in their 4 orthogonal neighbor cells.
4. Ray BlockingBlack walls completely block light beams, allowing bulbs on opposite sides of a wall to safely coexist.
Essential Akari Solving Techniques
- Start with Extremes (0s & 4s): A black block numbered “0” can never have any bulbs around it; immediately mark all adjacent cells with a dot. A “4” block must have bulbs in all four adjacent squares.
- Corner & Edge 3s: A “3” on an edge has only 3 available neighbors, meaning all 3 must be bulbs! Similarly, a “2” in an interior corner with only 2 white neighbors must be fully populated.
- Diagonal 3-3 and 1-1 Patterns: Two “3” walls sharing a diagonal corner force a bulb in the opposite corners, otherwise one of the 3s would be starved of valid placements.
- Dead-End Illumination: Look for isolated or narrow corridors that can only be lit from a single cell. Placing a bulb there is mandatory to prevent dark dead ends.