Look at these two pictures: a tiled bathroom floor and a honeycomb. What is the same about them? In each one, the shapes fit together with no gaps and no overlaps. Which shapes do you think can do that, and which ones leave a hole?

Look at the corner where shapes meet — that is where a shape either closes up neatly or leaves a hole. The interactive and the labelled picture show several shapes meeting at a point. Watch how many corners meet each time, and whether their angles make a full turn or fall short.

Now we fill an area together on the board with squares. As each square goes down, tell me whether the corner where it meets the others still adds up to a full turn. Each square corner is 90°, and four of them meeting make 360°, so the block fills with no gaps.

Before you design your own block, two ideas to name. First, the three ways we move a shape around a design: a translation slides it across without turning it, a reflection flips it like a mirror, and a rotation turns it around a point.