LITS: shapes and fits

List the tetrominoes that fit in a region and shade what they all share. Then rule fits out by the shapes next door.

This region is tight. Try every tetromino in it: only one fits.

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How it works

Every region holds exactly one tetromino. A lits fit is one place it could go. Most of LITS is ruling fits out until each region has one.

Overlap: cells that every remaining fit covers are shaded. Cells that no fit covers are unshaded. A small region often has a single fit.

Same shapes: the same-shape rule says two tetrominoes of the same letter never touch by an edge. A fit that would touch a finished tetromino of its own letter is out.

Neighbour check: a fit is out if it leaves a neighbouring region with no fit that works beside it.

Naming the shapes

Rotations and reflections count as the same shape. An L and its mirror image are both L. S and its mirror Z are both S.

So there are only four letters to track. Write the letter of each finished region in your head, and check neighbours against it.

Worth memorizing

Shade what every fit covers.
Dot what no fit covers.
Same letters can’t touch.
Mirror images count as the same letter.
Check fits against the neighbours.
A fit that leaves a neighbour no fit is out.

Practice

0 of 4 right

Question 1

What is the ringed cell?

Question 2

What is the ringed cell?

Question 3

What is the ringed cell?

Question 4

Using rules 1 to 4 only, what is the ringed cell?

Where you’ll use this

How to solve LITSAll the steps on one puzzle Blocks and connectionsThe next LITS technique Play LITSStart with the small regions

Play today’s LITSPut this lesson to work Next: LITS: blocks and connectionsNo 2×2 block may be all shaded, and the shading must be one piece. Both rules rule out fits, and when they run out, try a cell and see what breaks.