Bouncing balls in a concave bowl

What you are seeing: up to 1800 balls released at rest in the outline of a shape (a star, a heart, the letter A, a crescent moon), then shattered by gravity into a bowl whose profile you choose. On each contact the velocity is reflected about the local tangent and the normal component is scaled by the restitution $e$. The recognizable figure survives for a moment, then collapses: every ball follows the same simple law, so the shape dissolves into the bowl's natural motion. The bowl profile sets that motion: a parabola gives near-simple-harmonic swings, the V-bowl piecewise constant acceleration, the quartic a strongly amplitude-dependent period, the arc a pendulum. With $e = 1$ the balls bounce forever.