How to play Tetro Shade

Shade one piece of four connected squares (an L, I, T or S) in every region so that everything joins up, with no 2×2 blocks and no matching shapes touching. Also known as Tetromino shading puzzle, L-I-T-S puzzle.

▶ Play Tetro Shade ⊞ Open the solver

The rules

Every region contains exactly four shaded squares, joined side to side — a tetromino.
All shaded squares in the grid form a single connected group.
No 2×2 block of squares is completely shaded.
Two pieces of the same shape (counting rotations and reflections) may not touch along a side.

Playing Tetro Shade on Puzzle Solvers

Choose a size and a difficulty, then press New Puzzle.
Tap a square to shade it, again for a dot (white), again to clear. Drag to do several.
Finished pieces are coloured by shape — L, I, T or S — so matching pieces that touch stand out in red.
Hint explains the next deduction — pieces that only fit one way, 2×2 blocks, matching shapes and keeping everything joined.

Open the Tetro Shade game →

Using the Tetro Shade solver

Choose the size and draw the regions (or press Sample).
Press Solve and step through: ways a piece can fit, 2×2 blocks, matching shapes and connections.

Open the solver →

A worked example

A straight region of four squares is an I piece — so the neighbouring region can’t place an I piece against it.

An L-shaped region of five squares has only two ways to place four connected squares without making a 2×2 block — the squares common to both are shaded.

Strategies

Four-square regions. A region of exactly four squares is its own piece — shade it all.
Common squares. List the ways a piece can fit; a square used by every way is shaded.
2×2 watch. Three shaded squares in a 2×2 block make the fourth white.
Stay connected. A square whose whiteness would cut the shaded group in two must be shaded.
Shapes next door. Once you know a piece’s shape, the neighbouring piece across a border can’t be the same shape there.

Common mistakes

Shading a 2×2 block somewhere — even across two regions.
Leaving a piece cut off from the rest of the shaded squares.
Forgetting that a mirrored L is still an L.

Where it comes from

Tetromino region puzzles appeared in Japanese puzzle magazines in the early 2000s and are now a staple of puzzle championships.

Frequently asked questions

Are mirror images the same shape?

Yes — an L and a backwards L count as the same, and so do the two S shapes.

Can two different shapes touch?

Yes — only matching shapes may not share a side across a border.

Is there always one answer?

Yes — every puzzle here is checked to have exactly one solution.

How do I solve one from a book?

Open the Tetro Shade Solver, draw the regions and press Solve.

Keep going

All guides: How to play every puzzle and game.