ul li {
  list-style: none;
}

.sub-menu {
  display: none;
}

ul > li:hover .sub-menu {
  display: block;
}

a {
  text-decoration: none;
  color: inherit;
}

.main-menu li {
  background: #c22fef;
  color: aliceblue;
  border-radius: 2px;
  text-align: center;
}

.main-menu > li {
  width: 200px;
  border: 1px solid #77049a;
  margin: 1px 3px;
}

li:hover {
  background: #a93aca;
}

.sjx {
  border: 8px solid red;
  border-bottom-color: transparent;
  border-left-color: transparent;
  border-right-color: transparent;
  display: inline-block;
  justify-content: center;
  position: absolute;
  opacity: 0;
  right: 10%;
  transform: translateY(50%);
  transition: opacity 0.1s;
}

.main-menu li {
  position: relative;
}

ul > li:hover div {
  opacity: 1;
}