Don't Trap a Cell
A cell with only one free neighbour left would be sealed off if that neighbour were rejected too — so the neighbour is kept.
How it works
- 1The top-middle cell is rejected, so the top-left corner has just one way out left — the cell directly below it.
- 2If that cell were rejected too, the corner would be sealed in on every side. It could never be rejected itself (rejected cells can't touch), so it would sit there kept and cut off from every other kept cell.
- 3Kept cells must all connect, so the cell below the corner is kept.
- Kept
- Rejected
- Cells that establish the pattern
- Where the conclusion lands