box-shadow adds a shadow: box-shadow: 4px 4px 8px rgba(0,0,0,0.2). Use inset for inner shadows. Layer multiple shadows with commas. filter: drop-shadow() works on irregular shapes like transparent PNGs.
Shadows
/* box-shadow: x y blur spread color */
.card {
box-shadow: 0 2px 8px rgba(0,0,0,0.1);
box-shadow: 0 4px 20px rgba(0,0,0,0.15), /* layered */
0 1px 3px rgba(0,0,0,0.08);
}
/* Inset shadow (inside element) */
input:focus {
box-shadow: inset 0 2px 4px rgba(0,0,0,0.1);
}
/* Text shadow */
h1 {
text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}