Four springs

Everything moves on one of four springs, each a feeling:

spring	for
settle	the default: arrives quickly and rests without a wobble you could name
snap	what the hand does: toggles, presses, a knob meeting its end
drift	what lands: a card dealt, a stamp, a bookmark falling into place
glide	the large and the slow: sheets, pages, a morph across the screen

Each is physics (a stiffness and a damping, core/springs.js) simulated once and compiled to what CSS understands: a linear() curve and the time it takes to rest. core/springs.css keeps them as tokens (a test holds the two together), so a transition, a keyframe and a script move alike:

.thing { transition: transform var(--spring-snap); }

import { play } from './finmotion/core/finmotion.js';
play(el, [{ opacity: 0 }, { opacity: 1 }], 'drift');