#burst-12 {
    background: red;
    width: 80px;
    height: 80px;
    position: relative;
    text-align: center;
}
#burst-12:before, #burst-12:after {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    height: 80px;
    width: 80px;
    background: red;
}
#burst-12:before {
    -webkit-transform: rotate(30deg);
       -moz-transform: rotate(30deg);
        -ms-transform: rotate(30deg);
         -o-transform: rotate(30deg);
}
#burst-12:after {
    -webkit-transform: rotate(60deg);
       -moz-transform: rotate(60deg);
        -ms-transform: rotate(60deg);
         -o-transform: rotate(60deg);
}