Shade some cells, such that:
- the shaded cells within an area, if any, form a single tetromino
- all shaded cells are connected
- there is no 2-by-2 square consisting entirely of filled or unfilled cells
- no two of the same kind of tetromino touch along an edge (“Same” is up to rotation and reflection)
This differs from standard LITS in that some areas may remain empty, and the no-2-by-2 rule also applies to white cells.