Rules & objective
Each white island contains exactly one number and has that number of cells. Islands cannot touch orthogonally. All shaded sea cells connect, and no 2×2 square may be entirely sea.
Controls
Arrows select · Numbers enter · Backspace erases · U undoes
Worked example
A clue-three island contains exactly three edge-connected white cells. Different clue islands cannot merge, and the sea cannot contain a black 2×2 block.