The lanes of crates sit on a little hill above the waiting spots, and every crate has an imp of its color leaning on it, idling.
Tapping a lane: the front crate's imp shoves it with its back, levers it with a shovel or kicks it (one at random). The crate tumbles down the hill onto a waiting spot and lands with a puff of dust, and its door opens.
The imps climb out of the crate itself, hidden by it until they're past its open edge.
Stand-in drawings: the real leaning, kicking and rolling art is being made. The first crate sounds are in: a scrape, a shovel or a kick as the crate goes, and a crash as it lands.
TREASURE!