.speechbox {
  position: relative;
}

.speechbox::after {
  content: "";
  position: absolute;
  width: 0;
  height: 0;
  rotate: 180deg;
  top: 100%;
  left: 2em;
  border: 0.4rem solid transparent;
  border-top: none;
  border-bottom-color: #42dca3;
}