.rect-a {
  width: 30px;
  height: 50px;
  background-color: #ff0;
}
.rect-b {
  width: 30px;
  background-color: #ff0;
}
.rect-c {
  height: 50px;
  background-color: #ff0;
}
.rect-d {
  background-color: #ff0;
}
.rect-e {
  width: 30px;
  height: 50px;
}
.circle-a {
  width: 50px;
  height: 50px;
  border-radius: 50%;
  background-color: #ff0;
}
.circle-b {
  width: 50px;
  height: 50px;
  border-radius: 50%;
}
.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;
}