Don't Split the Board
Hard
Used by Smart Hint
All kept cells must stay connected — a cell whose rejection would cut the board into two separate regions has to be kept.
- Kept
- Rejected
- Cells that establish the pattern
- Where the conclusion lands
How it works
- Two cells are already rejected: the 3 in the top row, and the 3 at the start of the third row.
- Look at what that leaves in the top-left: three cells whose only route to the rest of the board runs through the single cell diagonally in from the corner.
- Reject that one cell as well and those three are cut off — a separate island of kept cells that can never rejoin the others, which the connection rule forbids.
- None of the three is trapped on its own, so nothing local gives this away — you have to follow the route out. The cell is kept.