Just Nurikabe

A Nurikabe board is a grid of numbers. You paint cells as sea until each number sits on an island of exactly that many cells, the sea joins up into one piece, and no 2×2 square is all sea. Just Nurikabe starts at the beginning. Five short steps cover the rules on small boards, one rule at a time. If you tap the wrong cell, the app tells you which rule it breaks. After that come nine lessons, from Ones and Finished Island through The Sea Must Connect to Common Ground and What If. Each lesson explains one deduction in plain words, works an example on a real board with the argument drawn in, and then gives you two positions to try yourself. A practice board built around that technique follows. When you get stuck in a game, the hint button works in steps. The first tap shows where to look. The second names the technique. The third draws the argument on your board. The cells are filled in…