Play Light Up (Akari) Online
Place light bulbs to illuminate every white cell. Numbered walls tell you exactly how many bulbs must be adjacent. No two bulbs may see each other!
Tap a white cell to place a bulb
What Is Light Up (Akari)?
Light Up, known in Japan as Akari (meaning “light” or “brightness”), is a logic puzzle created by the Japanese publisher Nikoli. It first appeared in 2001 and quickly became one of Nikoli’s most popular puzzle types alongside Sudoku, Kakuro, and Slitherlink.
The puzzle is played on a rectangular grid containing white cells and black walls. Some walls display a number. Your goal is simple yet challenging: place light bulbs (also called lamps) in white cells so that every white cell is illuminated while following a set of logical constraints.
Rules of Light Up
- Illuminate every cell: Every white cell must be lit, either by containing a bulb or by being in the same row or column as a bulb with no wall between them.
- No bulb conflicts: No two light bulbs may illuminate each other — they cannot share the same row or column unless a black wall separates them.
- Numbered walls: A black wall with a number (0–4) indicates exactly how many bulbs must be placed in the cells directly orthogonally adjacent (up, down, left, right) to that wall.
- Unnumbered walls: Black walls without numbers can have any number of adjacent bulbs — they provide no constraint.
- Unique solution: Every well-constructed Light Up puzzle has exactly one solution, reachable through pure logic without guessing.
How to Solve Light Up Puzzles
1. Start with Definite Placements
Look for numbered walls whose adjacent open cells exactly match the number. A 4-wall in the middle of the grid must have bulbs in all four adjacent cells. A wall showing 2 with exactly two open neighbours forces both to contain bulbs.
2. Use Zero Walls
A 0-wall means none of its adjacent cells can contain a bulb. You can mark these cells with an “X” to eliminate them. This often reveals forced placements nearby.
3. Look for Unreachable Cells
Find white cells that can only be illuminated from one direction. If a cell is surrounded by walls on three sides, the only way to light it is from the remaining direction — meaning a bulb must be placed somewhere along that line.
4. Eliminate by Contradiction
If placing a bulb in a cell would make it impossible to satisfy a nearby numbered wall, that cell cannot contain a bulb. Mark it with an X and move on.
5. Work from Corners and Edges
Corners and edges have fewer options, making them easier to resolve. A wall with a number in a corner has at most two adjacent cells, severely limiting possibilities.
6. Count Remaining Spaces
For numbered walls: if you’ve already placed some adjacent bulbs, count how many more are needed. If the remaining empty adjacent cells exactly match the remaining count, fill them all.
Grid Sizes & Difficulty Levels
- 7×7 — Easy: Quick puzzles ideal for beginners. Dense numbered walls provide many starting clues.
- 7×7 — Medium/Hard: Same small grid but fewer numbered walls, requiring more deduction steps.
- 10×10: The classic Akari size. A balanced challenge with room for complex light-path reasoning.
- 14×14: Large grids for experienced solvers. Longer solve times and deeper chains of logic.
Light Up vs Other Logic Puzzles
- vs Sudoku: Both are pure logic with no guessing, but Sudoku uses number placement while Light Up uses spatial reasoning about light paths.
- vs Nonograms: Nonograms reveal a picture; Light Up focuses on illumination coverage. Both use line-based logic.
- vs Minesweeper: Both have numbered clues affecting adjacent cells, but Minesweeper involves hidden information (mines), while Light Up is fully visible from the start.
- vs Slitherlink: Both are Nikoli puzzle types using constraint propagation. Slitherlink forms a loop; Light Up places bulbs.
Frequently Asked Questions
More Puzzle & Strategy Games
If you enjoy Light Up, try these other free games on our site: