{{short description|Logic puzzle typically played on a 10×10 board}} [[Image:LITS.png|thumb|right|Moderately difficult ''LITS'' puzzle (solution)]]
'''LITS''', formerly known as '''Nuruomino''' (ヌルオミノ), is a binary determination puzzle published by Nikoli.<ref>[https://web.archive.org/web/20080205125710/http://www.nikoli.co.jp/en/puzzles/lits/ Nikoli's English page on ''LITS'']</ref>
==Rules== ''LITS'' is played on a rectangular grid, typically 10×10; the grid is divided into polyominoes, none of which have fewer than four cells. The goal is to shade in a tetromino within each pre-printed polyomino in such a way that no two matching tetrominoes are orthogonally adjacent (with rotations and reflections counting as matching), and that the shaded cells form a valid nurikabe: they are all orthogonally contiguous (form a single polyomino) and contain no 2×2 square tetrominoes as subsets.
==History== The puzzle was first printed in ''Puzzle Communication Nikoli #106''; the original title is a combination of 'nuru' (Japanese: "to paint") and 'omino' (polyomino). In issue #112, the title was changed to the present one, which represents the four (of five) tetrominoes used in the puzzle: the L-shape, the straight, the T-shape, and the skew (square tetrominoes may never appear in the puzzle as they are a direct violation of the rule).
==Complexity== Testing whether a given LITS puzzle has a solution is NP-complete.<ref>{{citation|url=https://itn-web.it.liu.se/~chrsc91/papers/norinori-lits.pdf|contribution=Computational complexity and bounds for Norinori and LITS|first1=Michael|last1=Biro|first2=Christiane|last2=Schmidt|title=EuroCG 2017, Malmö, Sweden, April 5–7, 2017}}</ref>
==See also== *List of Nikoli puzzle types
==References== {{reflist}}
Category:Logic puzzles Category:Japanese board games {{puzzle-game-stub}}