How do you animate the
box-shadow property in CSS without causing re-paints on every frame, and heavily impacting the performance of your page? Short answer: you don't. Animating a change of
box-shadow will hurt performance.
There's an easy way of mimicking the same effect, however, with minimal re-paints, that should let your animations run at a solid 60 FPS: animate the
opacity of a pseudo-element.