Light Up (Akari) Solver

Edit · Play · Solve

Generate random solvable Light Up puzzles at any size from 3 × 3 to 25 × 25, or enter your own clues. Zoom in on larger boards to play comfortably on your phone.

Grid × same

Random difficulty

Tap to

Zoom to place bulbs on 20–25 grids; swipe sideways to move.

How to play

Choose a size and press 🎲 Random game.
The game automatically switches to Place bulbs / X marks. Tap a white square to place a 💡 bulb. Tap it again for an × (a reminder not to put a bulb there), then again to clear it.
Place bulbs until every white square is lit and all numbered clues are satisfied.
Press Check board to check your progress. Stuck? Use Solve puzzle to reveal a solution.

What do the black numbers mean?

A number tells you the exact number of bulbs directly touching that black square — above, below, left, or right. Diagonal bulbs do not count.

01234NoneOneTwoThreeFour

Example: A 0 forbids bulbs in the four directly touching squares, but a bulb diagonally beside it is allowed (provided it follows the other rules).

Remember: Bulbs shine in straight lines across white squares. Black squares stop the light. Two bulbs must never shine directly at each other.

See the rules with picture examples ↓

Load an example or create your own puzzle.

Import / copy puzzle text

One row per line: . white, # black, 0–4 numbered, B bulb, x no bulb. Rows must form a square grid.

Akari rules explained with pictures

These are small examples of parts of a puzzle, not full puzzle boards. Yellow means illuminated, 💡 is a bulb, a dark square is a wall or number, and × is an optional note that no bulb goes there.

1. Numbers count side-touching bulbs

This black 2 has exactly two bulbs directly next to it — one above and one left. Only up, down, left, and right count, never diagonals.

✓ Correct: two bulbs directly touch the 2.

2. Diagonal bulbs next to a 0 are allowed

A 0 means no bulbs touching its sides. The bulb at the upper-left corner is diagonal, so it does not count and is allowed.

✓ The diagonal bulb does not break the 0 clue.

3. Light travels in straight lines

Every bulb lights its own square and shines up, down, left, and right until a black square or the edge stops it. Light does not travel diagonally.

The black wall on the right stops the yellow light.

4. Bulbs cannot see each other

Two bulbs are not allowed in the same unobstructed row or column. A black square between them would block the light and make that pair possible.

✕ Wrong: these bulbs shine directly at each other.

To win: All white squares must be illuminated, every numbered wall must have its exact count of side-touching bulbs, and no two bulbs may shine at each other. × marks are only your notes — they do not block light. Black squares without numbers just block light.