p,span,button{color:#fff;display:block;&:focus{outline:solid black 2px;outline-offset:2px}}p{background-color:green}span{background-color:red}button{background-color:#00f}.a:before{content:"[.a]";background:#000;margin-right:1rem}.b:after{content:"[.b]";background:#000;margin-left:1rem}