HTML:

<div class="hamburger-menu">
  <div class="bar top"></div>
  <div class="bar middle"></div>
  <div class="bar bottom"></div>
</div>

CSS:

.hamburger-menu {
  display: flex;
  flex-flow: column wrap;
  justify-content: space-between;
  height: 2.5rem;
  width: 2.5rem;
  cursor: pointer;
}

.hamburger-menu .bar {
  height: 5px;
  background: black;
  border-radius: 5px;
  margin: 3px 0px;
  transform-origin: left;
  transition: all 0.5s;
}

.hamburger-menu:hover .top {
  transform: rotate(45deg);
}

.hamburger-menu:hover .middle {
  opacity: 0;
}

.hamburger-menu:hover .bottom {
  transform: rotate(-45deg);
}