Lights Out
Every press flips the light you pressed and the four around it. Clearing the board is easy to describe and much harder to do, because every fix breaks something else.
Lights on10
Size
- Status
- In play
- Presses
- 0
- Fewest possible
- 6
How to play
- Pressing a space flips it and its neighbours above, below, left and right.
- Pressing the same space twice puts everything back, so the order of your presses never matters, only which ones you make.
- The board is finished when every light is off.
- Every board is built by pressing a cleared board at random, so all of them can be cleared again.
- The counter shows the fewest presses that would clear the board you were given.
Questions
Can I get an impossible board?
No. Boards are made by pressing an empty one, and every press undoes itself when repeated, so a way back always exists.
Why is the fewest-possible number sometimes so low?
Because presses cancel. The generator may press twenty times and land on a board four presses from clear. The number shown is the true minimum, worked out by trying every possible top row.
Is there a trick?
Yes: light chasing. Clear the top row by pressing directly below any light still on, repeat down the board, and whatever survives on the bottom row tells you what the top row should have been.