LITS is a Nikoli puzzle genre, created by Naoki Inaba.
- Shade some cells in the grid.
- All shaded cells must be connected.
- No 2×2 square may be fully shaded.
- In every region, the shaded cells must form a single tetromino (that is, 4 connected cells).
- If two tetrominos (making up the shaded cells of a region) are adjacent, they must be distinct (considering rotation and reflection as equivalences).