What Is LITS? Rules, Example, and Beginner Tactics

What is LITS and how the puzzle works

The short answer to what is LITS is that it is a shading puzzle played on a rectangular grid already carved into irregular regions, a little like the walls of Nurikabe or the cages of a Killer Sudoku. In each region you shade exactly four connected cells so they form a tetromino, and the four legal shapes are the L, the I, the T, and the S, which is precisely where the name LITS comes from. Rotations and mirror images are allowed, so an L may point in any direction and an S can flip into a Z. Three global rules then bind all of those small shapes together. First, every shaded cell on the whole board must join into a single orthogonally connected group, so no piece is ever left stranded. Second, no 2x2 square anywhere may be completely shaded. Third, and most important, two tetrominoes of the same letter type may not touch edge to edge, even when they sit in different regions, which means an S pressed against a Z still breaks the rule because reflections count as the same type.

A short worked example

Picture a small region shaped like a plus sign with five cells. You cannot shade all five, because a tetromino is only four cells, so exactly one cell of that plus must stay white, and which cell you leave out decides both the letter you build and where it can reach its neighbors. If shading the top four cells would create a T that presses against another T in the region above, that option dies at once, and you are steered toward an L or an I instead. This is the whole feel of LITS: each region has only a handful of ways to hold a tetromino, and the connection rule, the no-2x2 rule, and the same-type rule quietly delete the illegal candidates one by one until a single survivor remains. Solving becomes a chain of these small eliminations rather than any single flash of insight, which is exactly what makes it so absorbing. A useful habit is to name each region's options aloud, since realizing a region can only be an L or an S immediately reveals which of its cells stay shaded no matter which shape ultimately wins.

Beginner tactics that actually help

• Start with the narrowest regions. A region only one cell wide can hold nothing but the I tetromino, which fixes four cells at once and anchors your connected group.
• Hunt for forced links. If a region can only reach the rest of the shaded shape through a single bottleneck cell, that cell is almost always shaded.
• Treat the 2x2 rule as an active tool. Whenever two shaded cells share a diagonal corner, remember that completing the square is illegal, which often forces a specific white cell nearby.
• Track letter types along borders. When an L hugs the wall of the next region, lightly note which shapes that neighbor may no longer form.
• Mark white cells too. Knowing a cell must stay unshaded is as powerful as shading one, because it trims a region down to its only legal tetromino.
• Revisit regions in passing. A tetromino locked in far across the board often removes the last ambiguity from a region you left with two candidates, so loop back instead of forcing an early choice.

How LITS compares to Sudoku

Sudoku and LITS share a clear family resemblance. Both are pure logic, both reward you for eliminating the impossible, and both should be solvable with no guessing at all. The difference is what you place. In Sudoku you drop symbols into cells under row, column, and box rules, while in LITS you do not fill every cell; instead you sculpt one connected shape from small standardized pieces under an adjacency rule. Sudoku thinking leans on counting and uniqueness, whereas LITS thinking leans on shape, contact, and flow, so a spell of LITS can sharpen a spatial muscle that number puzzles rarely touch. Learning what is LITS is a fine way to broaden the way you read a grid.

If that shape-first pleasure appeals to you, Shapedoku sits in a happy middle ground. It keeps the exact rules of classic Sudoku, but the nine values are nine glowing shapes instead of digits, so you reason with a triangle, a hexagon, a crescent moon, and a lotus rather than one through nine. Players who like coaxing pieces into their proper place also enjoy Mystic Sort, a calm sorting puzzle from the same studio. When you want familiar Sudoku logic wrapped in a more visual, cosmic feel, try Shapedoku at app.shapedoku.com, or print a few grids from shapedoku.com to solve away from a screen.