.burger {
  font-size: 0;
  position: relative;
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: column;
  flex-direction: column;
  -webkit-justify-content: center;
  justify-content: center;
  width: 20px;
  height: 20px;
}
.burger > span {
  width: 20px;
  height: 1px;
  background: var(--colour-two);
  transition: 0.2s ease;
}
.burger > span:nth-child(2) {
  transition: 0.2s margin ease;
  transition-delay: 0.2s;
  margin-top: 5px;
  margin-bottom: 5px;
}