old-v2-frontend/src/components/Header.css

.menu_icon [class*='menu_bar-'] {
  background: #fff;
  -webkit-transform: rotate(0deg);
  transform: rotate(0deg);
  -webkit-transition: 0.2s ease all;
  transition: 0.2s ease all;
  height: 0.18rem;
  display: block;
  margin-bottom: 0.3rem;
}

.menu_icon:focus {
  outline: 0;
}

.menu_bar-top {
  width: 25px;
}

.menu_bar-mid {
  width: 15px;
}

.menu_bar-bot {
  width: 20px;
}

.menu-opened .menu_bar-bot {
  width: 25px;
}

.menu-opened .menu_bar-top {
  -webkit-transform: rotate(45deg);
  transform: rotate(45deg);
  -webkit-transform-origin: 15% 15%;
  transform-origin: 15% 15%;
}

.menu-opened .menu_bar-mid {
  opacity: 0;
}

.menu-opened .menu_bar-bot {
  -webkit-transform: rotate(45deg);
  transform: rotate(-45deg);
  -webkit-transform-origin: 15% 95%;
  transform-origin: 15% 95%;
}

.panel:before {
  content: '';
  background-color: rgba(0, 0, 0, 0);
  transition: background-color 0.5s ease-in-out;
}

.panel-open:before {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 99;
}