<div class='clip-me'></div>

@import "compass/css3";

.clip-me {
  width: 300px; height: 300px;
  background: #222;
  
  clip-path: polygon(
    /* points of the outer triangle going counterclockwise */
    285px 150px, 83px 33px, 83px 267px, 

    /* return to the first point of the outer triangle */
    285px 150px, 

    /* points of the inner triangle going clockwise */
    258px 150px, 96px 244px, 96px 56px, 

    /* return to the first point of the inner triangle */
    258px 150px
  );
}