上三角 css

.dot-top {
  font-size: 0;
  line-height: 0;
  border- 10px;
  border-color: #1c1c52;
  border-top- 0;
  border-style: dashed;
  border-bottom-style: solid;
  border-left-color: transparent;
  border-right-color: transparent;
}