How to Solve Lights Out Puzzles: The Light Chasing Method, Explained

Lights Out is a classic grid puzzle, first sold as a handheld electronic game in 1995. The rules fit in one sentence, yet a random board can feel impossible. The good news: there is a simple, mechanical method that solves any solvable board, and once you understand why it works you will start seeing shortcuts on your own.

The rules

You get a grid of lights, classically 5×5. Some are on, some are off. Pressing a light toggles it and its four orthogonal neighbours (up, down, left and right). Lights on the edge simply have fewer neighbours. Your goal is to switch every light off.

Two facts that change everything

Before any strategy, two observations make the puzzle far less scary:

1. Order doesn’t matter. Pressing A then B gives exactly the same board as pressing B then A.
2. Pressing twice undoes itself. Press the same light twice and it is as if you never touched it.

Put together, a solution is not a sequence of moves. It is just a set of lights, each pressed once or not at all. That turns a scary search into something you can reason about.

Light chasing, step by step

The standard method is called light chasing:

1. Look at the top row. For every light that is on in row 1, press the light directly below it in row 2.
2. Row 1 is now completely dark. Move down: for every light still on in row 2, press the light directly below it in row 3.
3. Keep going, one row at a time, until you reach the bottom row.

Why it works: pressing a light in row 2 toggles the light directly above it in row 1, and nothing else in row 1. So each press in row 2 cleans up exactly one light in row 1. Later presses happen further down the board, so a row you have finished is never touched again.

Notice something else: once you decide what (if anything) to press in the top row, every other press is forced. The whole puzzle really comes down to the top row.

The bottom row problem

After chasing, every row is dark except, usually, the bottom one. There is no row below it to press, so you are stuck. The fix is to go back to the top row, press a specific set of lights there, and then chase all the way down again.

Which lights? It depends only on the pattern left in the bottom row. For the classic 5×5 board, numbering the positions 1 to 5 from left to right:

• Bottom row lights 1 and 5 left on: press 4 and 5 in the top row
• Lights 2 and 4: press 2 and 5
• Lights 1, 2 and 3: press 2
• Lights 3, 4 and 5: press 4
• Lights 1, 3 and 4: press 5
• Lights 2, 3 and 5: press 1
• Lights 1, 2, 4 and 5: press 3

Press those top row lights, chase down again, and the board goes dark.

If your leftover pattern is not on that list, the 5×5 board has no solution. That is not rare: only one in four of all possible 5×5 patterns can be solved. And every solvable 5×5 board has exactly four different solutions.

Why the lookup works: every press is a toggle, so effects simply add up. The extra top row presses change the final bottom row by a fixed amount, and the list above pairs each leftover pattern with the presses that cancel it.

The list is only for 5×5. Other sizes have their own, and you can build one yourself: on a dark board, press a single top row light, chase down, and write down the bottom row it leaves. Repeat for each top row position and combine the results.

Is light chasing the shortest solution?

Usually not. Chasing always finds a solution when one exists, but it can take far more presses than necessary, because it follows the rows mechanically instead of looking at the whole board.

Finding the shortest solution means comparing the possible solutions and picking the one with the fewest presses. Strong players also learn to spot shapes. The simplest one: when the five lights of a plus shape are lit, a single press in the middle clears all of them.

The three state variant

Some versions use tiles with three states instead of on and off. Each press moves the tile and its neighbours one step around a cycle: A becomes B, B becomes C, and C goes back to A. The same ideas still work, with small changes:

• Order still doesn’t matter.
• Three presses do nothing, so each tile gets pressed zero, one or two times.
• Chasing still works: choose a target state. For each tile in row 1 that is not on target, press the tile below it once or twice, whatever it takes to bring it around.
• The bottom row can still be left over, and the fix is still in the top row. Each top row tile now has three choices, so the lookup grows bigger.

If the goal is simply “make every tile the same”, you get a bonus: you can try each possible target state and keep whichever works out shortest.

Under the hood, both versions are solved with linear algebra, using arithmetic that wraps around at 2 or 3. That is how puzzle designers check that a level is solvable and work out its true minimum number of moves.

Furzzle: the classic, with dogs, cats and bunnies

Furzzle is our cozy spin on this classic. Instead of lights, the tiles are adorable animals. Tap a tile and it flips to the next animal, along with its four neighbours: 🐶 → 🐱 → 🐰 → 🐶. To win, make the whole board the same animal, any animal you like.

Early worlds use just dogs and cats, the two state version. Later worlds add bunnies, the three state version, and boards grow from 3×3 all the way up to 7×7. Every level is proven solvable, and every level has a known minimum number of moves, computed with the same math described above. When you clear a level you see your moves next to that minimum.

Light chasing will carry you through plenty of boards. Matching the minimum is where it gets interesting.

Want to try it? Play today’s Daily Furzzle in your browser with no install needed, or get Furzzle on Google Play for all the worlds.