.triangle-a {
  display: inline-block;
  width: 0;
  height: 0;
  border: solid transparent;
  border-width: 5px;
  border-bottom-color: #ff0;
}
.triangle-b {
  display: inline-block;
  width: 0;
  height: 0;
  border: solid transparent;
  border-width: 5px;
  border-top-color: #ff0;
}
.triangle-c {
  display: inline-block;
  width: 0;
  height: 0;
  border: solid transparent;
  border-width: 5px;
  border-right-color: #ff0;
}
.triangle-d {
  display: inline-block;
  width: 0;
  height: 0;
  border: solid transparent;
  border-width: 5px;
  border-left-color: #ff0;
}