怎么统一写个background-size ,而又不会被后面的background的简写覆盖?

Question

div{background-size: 50% auto}
div.a{background: url(../images/a.png) no-repeat left top}
div.b{background: url(../images/b.png) no-repeat left top}

想让这个background-size只写一次,而后面的又用简写的方式,该怎么写?
最好不用 !important

Answer 1

div { background: transparent no-repeat left top; background-size: 50% auto; }
div.a { background-image: url(../images/a.png); }
div.b { background-image: url(../images/b.png); }