Shade in tetrominoes such that the black cells are all connected to each
other through their edges, and no 2x2 cell area within the grid
contains all black cells. No two congruent tetrominoes may share an
edge, even if they are rotated or reflected versions of each other.
Numbers in a cell indicate the sizes of the orthogonally contiguous
groups formed by black cells sharing a corner or an edge with that cell.
For example, "3" means that the cell shares a corner or an edge with
three black cells, and they form a single group, whereas "1 3" means the
cell shares a corner with four black cells which form a group of three
cells and a single separate cell. Cells with numbers cannot be black.