Box shadow generator

Real shadows are soft near the object and fade out further away. Stacking two or three shadows with growing blur and falling opacity looks far more natural than one big blurry shadow.

Spread grows or shrinks the shadow before it is blurred; a negative spread keeps a large blur tight under the element. Inset draws the shadow inside the box, which makes it look pressed in.

A few static shadows are fine. Animating large, very blurry shadows can make scrolling stutter on weak phones. Animate opacity of a shadowed layer instead.