Particles
A hundred thousand embers riding a wind you can bend
A hundred thousand embers riding a turbulent wind, drawn as a long exposure that never quite forgets — the trails are history and the colour is speed. The streams braid and circulate instead of pooling. The pointer is a vortex that gathers the swarm; push its charge below zero and it scatters instead.
Rendering cost: medium. A few dozen samples per pixel: comfortable fullscreen on a discrete GPU, but cap the pixel ratio for a retina hero. How to tune it
Take Particles with you.
Particles is free. Sign in and it is yours — the background itself, with your settings already saved in, ready to drop into your site. The account is only somewhere to put the files. No card now, and no card later.
The other 61 come with a licence, $9.99 once.
$0forever
Your preset is in the URL. It survives the trip.