yagni.css/src/_background-size.css

yagni.css - collection of atomic css declarations to be embedded to your project using postcss

.bg-size-cover   { background-size: cover; }
.bg-size-contain { background-size: contain; }
.bg-size-auto    { background-size: auto; }
.bg-size-unset   { background-size: unset; }