Cardfall

each bounce keeps the same fraction of the speed.

the old solitaire win sweep, left on the table: arches that shrink by the same ratio every bounce

A bouncing card never gets its full speed back -- the bottom edge returns a fixed fraction of it every time, a number called the coefficient of restitution. Because how high something rises depends on speed squared, that fixed fraction of speed becomes a fixed RATIO between one arch and the next, so they shrink geometrically rather than by some constant amount. The horizontal speed, meanwhile, never changes at all, which is why the arches march evenly across the table while getting shorter. The old solitaire win animation was this, and it left every position on screen -- so the whole decay curve stayed there to be read, which is what this does too.

Concepts: restitution, energy, bouncing.

An interactive you play with one thumb, on Wundr.