GridWits
Medium tier Technique 11 of 18 Used by Smart Hint

Sea Connectivity

If a cell becoming land would cut the sea into two pieces that could never reconnect, it stays sea.

How it works

  1. 1All of the water on a finished board has to join up into one region.
  2. 2The sea cell in the top-left corner has only two ways out, and the 1 directly below it is land forever.
  3. 3If the cell to its right became land too, that corner would be walled off from the rest of the sea with no way back.
  4. 4So that cell stays sea.
1 4
  • Sea
  • Cells that establish the pattern
  • Where the conclusion lands
Next in the ladder Completion Pool →

A cell touching an island one short of its size would finish it — and a finished island is walled in sea on every side. If that walling would trap a 2×2 pool, the cell can't be land after all: it's sea.