Ages
By age.
What a child does with wood, year by year.
Birth to one
Mouthing and grasping. The Ring Stack and the smallest arches.
One to two
Stacking and knocking down. The Arch Set, the Pull Duck for the first walk.
Two to four
Building and pretending. The Block Box joins the arches.
Four to six
Bridges, towns, marble runs. Everything at once.
Start with the arches.
They join every set that follows.