LITS is a Japanese logic puzzle published by Nikoli. The name comes from the four tetromino pieces permitted in the game: L, I, T, and S. Players shade one tetromino in each region while obeying adjacency and connectivity rules.

Is the 2x2 square tetromino (O) allowed in LITS?

No! The square 'O' tetromino is strictly forbidden. Furthermore, no 2x2 square of shaded cells may appear anywhere on the entire grid.

Can two identical tetrominoes touch?

No two congruent tetrominoes (even rotated or mirrored, such as L and J, or S and Z) may touch orthogonally. They may only touch diagonally.

Must all shaded cells be connected?

Yes. All shaded cells across the entire grid must form a single continuous orthogonally connected group.

How many cells are shaded per region?

Exactly four cells must be shaded in each outlined region.

LITS is a Japanese logic puzzle published by Nikoli. The name comes from the four tetromino pieces permitted in the game: L, I, T, and S. Players shade one tetromino in each region while obeying adjacency and connectivity rules.

Is the 2x2 square tetromino (O) allowed in LITS?

No! The square 'O' tetromino is strictly forbidden. Furthermore, no 2x2 square of shaded cells may appear anywhere on the entire grid.

Can two identical tetrominoes touch?

No two congruent tetrominoes (even rotated or mirrored, such as L and J, or S and Z) may touch orthogonally. They may only touch diagonally.

Must all shaded cells be connected?

Yes. All shaded cells across the entire grid must form a single continuous orthogonally connected group.

How many cells are shaded per region?

Exactly four cells must be shaded in each outlined region.

Nikoli Classic • Tetromino Regions

LITS (Tetrominoes)

Place the legendary tetrominoes! Shade an L, I, T, or S in every outlined region such that identical shapes never touch and all blocks link into a single body.

5x5 LITS Quadrant5x5 Grid • 4 Regions (1 Tetromino Each)

0:00

0/4 tetrominoes formed

R1:0/4

R2:0/4

R3:0/4

R4:0/4

Click Tool:

Shapes: L, I, T, S (O is forbidden)

Fitting tetrominoes...

LITS Rules & Tetromino Architecture

Published by Nikoli in 2004, LITS turns classical polyominoes into a deductive balancing act:

1. One Tetromino Per RegionShade exactly 4 cells per region to form an L, I, T, or S (rotations & reflections allowed). The 'O' block is forbidden!

2. Congruence BanTwo matching tetrominoes (such as two Ls or two Ts) can NEVER share an edge, even across region boundaries!

3. Unified Shaded NetworkAll shaded cells on the board must form a single continuous orthogonally connected body.

4. Zero 2x2 PoolsA $2\times2$ square of shaded cells is completely prohibited anywhere on the grid.

Master Deductive Tactics

1. Instant Size-4 Regions

Always inspect regions of size 4 first! In any region containing exactly 4 cells, all 4 cells must be shaded. Immediately identify its tetromino type and propagate bans to all bordering regions!

2. Neighboring Shape Elimination

If Region A is confirmed to be an 'L' tetromino, no adjacent cell in neighboring Region B can form an 'L' if it would touch Region A. This rapidly eliminates possible orientations in adjacent rooms.

3. 2x2 Pool Prevention

Whenever three cells of a $2\times2$ square are shaded, the fourth cell must remain unshaded (✕). Use this rule to cut off illegal square formations instantly.

4. Single-Bridge Connectivity

If an outer region has only one cell bordering the rest of the shaded network, that cell must be shaded to connect the region's tetromino to the rest of the board!

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