Island Sea· Advanced

Goal

Fill all empty cells as either island (light) or sea (dark) to complete the puzzle.

How to Play

  • Tap an empty cell to paint it as sea (dark)
  • Tap a sea cell again to mark it as island (light)
  • Tap an island cell once more to clear it

Number = Island Size

Each numbered cell belongs to an island with exactly that many cells. Different islands cannot touch orthogonally.

OK3
NG3

Sea Must Be Connected

All sea cells must form one connected group with no gaps. Also, sea cells cannot form a 2×2 square.

OK1
NG2

Completed Example

  • Numbers indicate the size of their island (count of connected cells)
  • Different islands cannot be orthogonally adjacent
  • All sea cells must form one connected group
  • Sea cells cannot form a 2×2 square (no pools)
2131

Tip

  • Start with cells numbered 1 — all 4 surrounding cells must be sea
  • If 3 sea cells form an L-shape, the 4th cell must be island (no 2×2 sea allowed)
  • Compare each island's number with remaining empty neighbors to find forced cells

Island Sea puzzles train spatial reasoning, path connectivity analysis, and constraint satisfaction problem (CSP) solving skills. Research shows that spatial cognition puzzles improve visuospatial working memory and problem-solving abilities.

  • Uttal, D. H., et al. (2013). "The malleability of spatial skills: A meta-analysis of training studies." Psychological Bulletin, 139(2), 352-402.
  • Miyake, A., et al. (2001). "How are visuospatial working memory, executive functioning, and spatial abilities related?" J. Exp. Psychol. Gen., 130(4), 621-640.