Contradiction
Extreme
Used by Smart Hint
When nothing else advances the puzzle, try one cell's two possible states and follow the consequences a few steps ahead. If one choice breaks a rule, the other is forced.
- Cells that establish the pattern
How it works
- When every other technique is stuck, pick any undecided cell and try one of its two possible states — land or sea.
- Follow the consequences forward a few steps — the same techniques above, applied to what that one choice forces next.
- If within a handful of steps some island ends up impossible to complete, the sea traps itself, or a 2×2 block forms, that choice can't be right.
- The cell is forced to the OTHER state instead — no different, in spirit, from a person saying "if this were sea, that island over there could never reach its number — so it isn't." The search only ever looks a few steps ahead, matching what a person could actually trace by hand.