Giant Polydron Vehicle Builders Set

Wheels change everything. Add them to Giant Polydron and the thing your child just built can be pushed across the floor — a tractor, a bus, a hot rod, whatever they've decided it is.

The wheels rotate freely and come in two sizes, with the big ones measuring 36cm across. There's a picture guide in the box, though most children ignore it fairly quickly and make their own thing.

Movement, cause and effect, and the small triumph of watching something you made actually roll.