Switch Off Strategy: The Chasing Method
1. Chase the lights down
Look at the top row. For each light that's on, press the light directly below it. The top row is now off. Repeat with the second row, and so on. After the last step only the bottom row can still be lit.
2. Read the bottom row
The bottom row now shows a pattern. Each pattern needs a particular set of presses in the top row. On 5×5, for example:
| Bottom row lit | Press in the top row |
|---|---|
| 1, 2, 3 | 2 |
| 1, 2, 4, 5 | 1 |
| 1, 3, 4 | 4 |
| 1, 5 | 1, 2 |
| 2, 3, 5 | 5 |
| 2, 4 | 1, 4 |
| 3, 4, 5 | 4 |
3. Chase again
After those top-row presses, chase the lights down once more. The board goes dark.
4. Fewer presses
Chasing always works but isn't always shortest. Pressing a light twice cancels out, so if your plan presses a light twice, drop both. The hint shows a shortest solution.
Frequently asked questions
What is light chasing?
Work down the board: for every lit light in a row, press the light directly below it. That turns off everything except the bottom row. Then a fixed pattern of presses in the top row, followed by chasing again, clears the rest.
Last updated 2026-10-20