We define an orthogonally contiguous shape to be a shape in which there is a path between every two squares in it using only vertical and horizontal lines, and going only through squares that are part of the shape.
In each bordered area, shade some cells so that exactly 4 squares in that area remain unshaded -- those 4 squares must be orthogonally contiguous (a tetromino). No two identical unshaded tetrominoes (from different areas) can touch orthogonally (mirrors and rotations are considered identical); but they can touch diagonally -- that is, they cannot share an edge of a cell, but they can share a corner of a cell. After you are done, the shaded squares should form a single orthogonally contiguous shape, with no 2X2 squares in it.
The puzzle has a single solution.