How to Solve Akari (Light Up): A Beginner’s Guide for Adults
To solve an Akari (Light Up) puzzle, place light bulbs in white squares so every cell is lit, no bulb shines directly on another, and each numbered black square has exactly that many bulbs touching its sides. Start with the easy clues — a black 4 needs bulbs on all four sides — and the rest follows by logic, not guessing.
What Is Akari (Light Up)?
If you have looked at a grid of white and black squares, spotted the numbers on some of those black squares, and thought “I see the bulb icon but I have no idea where it goes,” you are in the same place most beginners start. That hesitation is reasonable. The puzzle looks static and a little blank — until its one core rule clicks and the whole grid lights up.
Akari — also known in English as Light Up, and published in Japan as 美術&#館; (bijutsukan, “art gallery”) — is a logic puzzle created by the Japanese publisher Nikoli. The name Akari (明かり) simply means “light.” That origin is context only; the puzzle itself requires nothing cultural, only careful observation.
The setup is straightforward: a rectangular grid of white and black cells. Your job is to place light bulbs in white squares. Each bulb shines horizontally and vertically, illuminating every cell in its row and column until a black cell blocks the beam. When you are done, every single white cell must be lit — either by holding a bulb itself, or by sitting in the path of one.
Quick vocabulary: the squares that hold bulbs are white cells, the barriers are black cells, and the numbers on some black cells tell you exactly how many bulbs must sit directly beside them.
The Rules of Akari (in Plain English)
According to Wikipedia’s article on Light Up, the rules break down cleanly into four points.
- Place light bulbs only in white cells. Bulbs never go on black cells or outside the grid.
- A bulb illuminates its entire row and column — from one black cell (or wall) to the next. Every white cell in that path is considered lit.
- No two bulbs may shine on each other. If two bulbs are in the same row or column with no black cell between them, that placement is illegal. This is the constraint beginners most often overlook.
- Every numbered black cell must have exactly that many bulbs touching its four sides. A “2” means two of its four adjacent white cells hold bulbs. Diagonal neighbors do not count.
One extra note: black cells without a number carry no constraint at all — they simply block light and divide the grid.
Quick worked example: a black cell marked “2” sits in the middle of the grid with white cells above, below, left, and right. Exactly two of those four neighbors must hold bulbs. The puzzle gives you other clues to decide which two — and that reasoning is the heart of Akari.
Where Do You Start? Begin with the 4s and Walled-In Numbers
Those black squares with numbers are not a guessing game. You can place every bulb with simple logic — and the easiest place to start is staring right at you: a black 4, or a number backed into a wall.
Start with the 4. A “4” means all four adjacent cells must hold bulbs. There is no choice, no reasoning required. The moment you see a 4, place bulbs on every white neighbor immediately. That one move can illuminate a large portion of the grid and eliminate candidate positions in the surrounding rows and columns.
Look for walled-in numbers. A “3” pressed against a wall has only three reachable neighbors — one direction is already blocked by the edge of the grid. All three must hold bulbs. A “2” tucked into a corner has only two accessible neighbors, so both are confirmed at once. The fewer open neighbors a number has, the more it tells you.
Apply the 0 rule. A “0” means no bulb may touch that black cell on any of its four sides. Mark those adjacent cells with a small dot to show they cannot hold a bulb. Each dot is a ruled-out position — and ruled-out positions clarify what remains.
Placing bulbs next to a “0” is a common error. The dot-marking habit stops that mistake before it starts.
A black “4” requires a bulb on all four sides — no reasoning needed. Place those bulbs first, then let the illuminated rows and columns narrow down what comes next.
The Diagonal Trick: Why a 3 or 4 Blocks Its Own Corners
This is the move most beginners miss — and once you see it, it opens grids faster than any other technique.
The core insight: a black cell marked “3” needs three of its four adjacent cells to hold bulbs. If you place a bulb in one of its diagonal neighbors instead, that diagonal bulb does not count toward the “3” requirement — yet it occupies a cell in the same row or column as one of the real adjacent cells, which would prevent a bulb from sitting there. Place a bulb diagonally and you make it impossible to satisfy the “3.”
In practice: when you see a 3 or 4, mentally mark its four diagonal corners as cells that cannot hold bulbs. Add a dot to each. This eliminates those positions before you have reasoned through anything else.
Forced illumination. Once cells are ruled out, look for white cells that are still unlit and have only one remaining candidate position — the only cell from which a bulb could possibly reach them. When a white cell has exactly one candidate, that candidate is confirmed. Place the bulb.
Work in this order: high-number clues first, diagonals and 0-adjacent cells second, then scan for forced illumination.
A bulb in the diagonal corner of a 3 or 4 cannot count toward the requirement — and it blocks the real adjacent cells. Rule out all four diagonal corners with a dot as soon as you find a 3 or 4.
Stuck? Use the “No Two Bulbs” Rule and Mark the Dots
Every solver reaches a point where no move looks obvious. Three habits keep the puzzle moving.
1. Apply the no-two-bulbs rule actively. Every bulb rules out its entire unobstructed row and column — mark those cells with a dot after each placement and the candidate pool shrinks quickly.
2. Trust your dot marks. When a white cell is unlit and every candidate position except one is dotted out, the remaining position is confirmed. Dot marks convert stalling into progress.
3. Check every unlit cell. Scan for white cells that are still dark and ask which single cell could illuminate them. If the answer is zero candidates, retrace from the last certain move.
After each placement, dot out the cells in that bulb’s row and column. Ruled-out cells are progress — they narrow the grid toward the next confirmed move.
Getting Better at Akari
The fastest way to build fluency is to start with small grids. A 5×5 Akari typically has only a handful of numbered black cells and can be solved in two or three minutes once the 4-first and diagonal-trick habits are in place. Spend a few sessions on small grids before moving to 7×7 or larger.
Find a puzzle source — an Akari app, a puzzle book, or a free printable grid — and work through one puzzle each day. The rules stay identical at every size; what grows is your ability to spot high-number clues and walled-in configurations at a glance.
If you enjoy step-by-step logic puzzles, similar reasoning carries into other formats: how to solve Slitherlink uses a closed-loop counting structure, how to solve Hashi applies forced-move logic to numbered islands, and how to solve nonograms builds the same ruled-out-cells habit on a picture grid. Newer to logic puzzles? how to get better at Sudoku is the clearest entry point in the series.
If you enjoy a quick number warm-up between logic sessions, Make 10 keeps number-sense active. It is not an Akari solver — it is a different kind of puzzle where you connect tiles so their values add up to ten. No download, no account, plays in your browser in seconds.
Frequently Asked Questions
What is the goal of Akari (Light Up)?
Place light bulbs in white squares so that every white cell in the grid is illuminated. A bulb lights its entire row and column until a black cell blocks the beam. The puzzle is solved when every white cell is lit and no two bulbs shine directly on each other.
What do the numbers on the black squares mean?
The number tells you how many bulbs must sit directly beside that black cell — touching one of its four sides. A “3” means three of its four adjacent cells hold bulbs. Diagonal neighbors do not count. A black cell with no number carries no restriction.
Where should I start an Akari puzzle?
Start with the highest numbers. A “4” forces bulbs on all four sides immediately. A “3” or “2” against a wall has only as many open neighbors as the number requires — all are confirmed at once. Then apply the 0 rule to mark cells that cannot hold a bulb.
Can two light bulbs be in the same row?
Yes, if a black cell separates them. Two bulbs in the same row or column are legal as long as there is at least one black cell between them, blocking the light path. If no black cell sits between two bulbs in the same line, that placement is illegal.
Is Akari based on math or logic?
Logic, not arithmetic. The numbers are counts of adjacent bulbs — not values to add or subtract. The required skill is spatial reasoning: tracking which cells are illuminated, which positions are ruled out, and where a bulb is the only remaining option. A satisfying logic challenge, not a math test.
More from the Make10s blog: how to solve Slitherlink · how to solve Hashi · how to solve nonograms · how to get better at Sudoku · all posts
Sources: Wikipedia — Light Up (puzzle) · puzzle-light-up.com
Just for fun — not medical advice.