CSS - left triangle shape

Question

&:before {
  position: absolute;
  left: -16px;
  top: -30px;
  content: "";
  display: block;
  z-index: -1;
  width: 0;
  height: 0;
  border-top: 80px solid #bbd5f9;
  border-right: 80px solid transparent;
  @media (max-width: $coworking_tablet) {
      left: -20px;
      top: -20px;
      border-top: 65px solid #bbd5f9;
      border-right: 65px solid transparent;
  }
  @media (max-width: $coworking_mobile) {
      left: -15px;
      top: -9px;
      border-top: 45px solid #bbd5f9;
      border-right: 45px solid transparent;
  }
}