What Is Akari? Light Up Rules, Tactics, and a Worked Example

What is Akari, exactly?

What is Akari? Also known as Light Up, Akari is a bright little logic puzzle where you place light bulbs on a grid until every white cell is illuminated. The board is a mix of white cells and black wall cells, and some of those walls carry a number. A bulb shines along its own row and column until a wall blocks the light, so a single well-placed bulb can light a whole corridor. Akari is beloved because its rules are tiny yet its deductions can be delightfully tricky, and it looks cheerful on the page. If you like puzzles that reward careful counting and clean lines of sight, Akari is an easy one to fall for during a quiet break.

The rules of Akari

The rules of Akari are short. You place light bulbs in white cells, and each bulb lights up its own cell plus every cell in the same row and column until the beam meets a black wall or the edge of the grid. First, every white cell must end up lit. Second, no bulb may shine onto another bulb, which means two bulbs can never sit in the same row or column with a clear path between them. Third, a numbered wall must have exactly that many bulbs in the white cells directly adjacent to it, counting only up, down, left, and right. Black walls without a number simply block light and carry no bulb requirement. When every white cell is lit and no bulbs see each other, the puzzle is solved.

Here is a worked example. A wall labeled four is the friendliest clue in the game: it demands bulbs in all four of its orthogonal neighbors, so you can place them instantly. A wall labeled zero is just as helpful in reverse, since it forbids bulbs in every adjacent cell, letting you cross those off. Now picture a white cell tucked against walls on three sides with only one open direction. If nothing can light it from that single open line, then the cell itself must hold a bulb. Chaining these forced placements together, while respecting the rule that no two bulbs may see each other, quickly turns a scattered grid into a fully lit room without a single guess.

Beginner tactics for Akari

• Place bulbs around four and zero walls first, because those clues are completely forced and never ambiguous.
• Find white cells that can be lit only one way, and put a bulb in the sole cell that can reach them.
• Remember bulbs cannot see each other, so a bulb blocks its own row and column for any other bulb until a wall intervenes.
• Use walls as blockers to plan sight lines, splitting long rows and columns into separate lightable segments.
• Recount numbered walls after every placement to confirm they hold exactly the required number of adjacent bulbs.

How Akari compares to Sudoku

Next to Sudoku, Akari looks and feels quite different, yet the mental muscles overlap. Sudoku is about placing each of nine symbols once per row, column, and box through elimination, while Akari is about covering a grid with light under strict adjacency and sight-line rules. Both share the reassuring promise of one solution reachable by logic alone, with no guessing needed. If Akari has you enjoying that bright, click-into-place feeling, you might also like Star Bolts, a snappy arcade game from the studio behind Shapedoku. And when you want to return to classic every-symbol-once solving with a calm, cosmic mood, Shapedoku replaces Sudoku numbers with nine glowing shapes you can read by color and form. It is colorblind-friendly by design, with a free solver and printable puzzles at shapedoku.com and instant browser play at app.shapedoku.com.