<style type="text/css">
#twelve-point-star {
   height: 100px;
   width: 100px;
   background: orange;
   position: absolute;
   color:#fff;
}


#twelve-point-star:before {
   height: 100px;
   width: 100px;
   background: orange;
   content:"";
   position: absolute;
   /* Rotate */
   -moz-transform: rotate(30deg);
   -webkit-transform: rotate(30deg);
   -ms-transform: rotate(30deg);
   -o-transform: rotate(30deg);
   transform: rotate(30deg);
}


#twelve-point-star:after {
   height: 100px;
   width: 100px;
   background: orange;
   content:"";
   position: absolute;
   /* Rotate */
   -moz-transform: rotate(-30deg);
   -webkit-transform: rotate(-30deg);
   -ms-transform: rotate(-30deg);
   -o-transform: rotate(-30deg);
   transform: rotate(-30deg);
}
</style>

<div id="twelve-point-star">

これがどうした。

</div>