Snowball
only what is smaller than you will stick. so grow.
a snowball on a field of scattered things: only what is smaller than you sticks, and every stick makes you bigger
A snowball picks up anything smaller than it, and everything it picks up makes it bigger, so the next size up becomes takeable: growth feeding on growth. Something over the line stops the ball until it grows past it.
Concepts: scaling, feedback-loops.
An interactive you play with one thumb, on Wundr.