How to Solve a 5×5 Light Up (Akari) Puzzle, Step by Step

The fastest way to learn Light Up — the puzzle also called Akari — isn't to reread the rules; it's to watch one get solved, one forced move at a time, with nothing skipped. So that's what this is: a complete walkthrough of a single 5×5 Light Up puzzle, from the clues to the fully lit grid. The 5×5 is the smallest size, which makes it the perfect place to learn — big enough to use the core techniques, small enough to follow every step. Grab a pencil and follow along, then play a 5×5 Light Up puzzle of your own. New to the rules? Our how-to-play guide covers them first.

The puzzle

Here's our grid. The shaded cells are walls; the numbers on them are clues telling us how many light bulbs must sit directly beside that wall. Every other cell is open and starts empty. A dot (·) marks an open cell.

	C1	C2	C3	C4	C5
R1	0	·	·	·	0
R2	·	·	·	·	·
R3	·	·	4	·	·
R4	·	·	·	·	·
R5	0	·	·	·	0

Our job: place light bulbs in the open cells so that every open cell is lit, no two bulbs shine on each other, and each numbered wall has exactly that many bulbs touching it. Remember, a bulb lights its whole row and column until a wall or the grid edge stops it. We'll name cells by Row and Column — so R2C3 is row 2, column 3.

Step 1: Clear the four 0-walls

Start with the easiest clue in the puzzle: the 0 walls sitting in all four corners. A 0 means no bulb may touch this wall, so we cross out (mark "no bulb") every cell next to each corner:

• The corner at R1C1 rules out R1C2 and R2C1.
• The corner at R1C5 rules out R1C4 and R2C5.
• The corner at R5C1 rules out R5C2 and R4C1.
• The corner at R5C5 rules out R5C4 and R4C5.

Eight cells eliminated already, before we've placed a single bulb. Always start with the 0-walls.

Step 2: The 4-wall forces four bulbs

Now the powerful clue: the 4 on the wall at R3C3. A 4 means all four of its orthogonal neighbours must be bulbs. So we place light bulbs at:

R2C3, R4C3, R3C2, and R3C4.

That's four bulbs in one move — and notice the elegance of it. The wall sits between the top and bottom bulbs (R2C3 and R4C3) and between the left and right bulbs (R3C2 and R3C4), so neither pair can shine on the other. The clue is self-consistent.

	C1	C2	C3	C4	C5
R1	0	·	·	·	0
R2	·	·	💡	·	·
R3	·	💡	4	💡	·
R4	·	·	💡	·	·
R5	0	·	·	·	0

Step 3: Trace the light

Now follow each bulb's rays — every bulb lights its row and column until it hits a wall or the edge:

• R2C3 lights all of row 2 (R2C1–R2C5) and, in column 3, up to R1C3. It can't shine down past the wall at R3C3.
• R4C3 lights all of row 4 and, in column 3, down to R5C3.
• R3C2 lights leftward to R3C1 and, in column 2, the whole column: R1C2, R2C2, R4C2, R5C2.
• R3C4 lights rightward to R3C5 and, in column 4, the whole column: R1C4, R2C4, R4C4, R5C4.

Check every open cell against those rays and you'll find every single one is now lit. The four corner cells are walls, so they don't need lighting — and the four bulbs between them reach everything else.

Step 4: Confirm the solution

A Light Up puzzle is solved when all three rules hold. Let's verify:

• Every open cell is lit? Yes — traced in Step 3.
• No two bulbs shine on each other? The only bulbs that share a line are R2C3/R4C3 (split by the wall) and R3C2/R3C4 (split by the wall). None can see another. ✓
• Numbered walls satisfied? The centre 4-wall has exactly four bulbs beside it. Each corner 0-wall has none. ✓

The grid is fully lit, conflict-free, and every clue is satisfied. Solved — with no guessing anywhere.

What you just learned

Look at the order we used: 0-walls first to eliminate cells for free, then the 4-wall to force bulbs, then light-ray tracing to confirm illumination, and finally the completion check. That's the exact toolkit you'll use on every Light Up puzzle, at any size. The bigger 7×7, 10×10, and 14×14 grids simply have more steps — and fewer generous clues, so you lean more on the illumination logic — but the moves are the same.

The only way to make it stick is to do it yourself. Play a 5×5 Light Up puzzle now, start with the 0-walls, and watch the grid light up. When you're ready for the trickier deductions, our full strategy guide and our numbered-walls guide take these ideas further.