header {
  height: 100px;
  width: 100vw;
  position: fixed;
  top: 0;
  left: 0;
  background-color: transparent;
  z-index: 3;
  transition: background-color 0.5s;
  padding-left: 15px;
  display: flex;
  align-items: center;
}

header.scrolled {
  background-color: #1d1d1f;
}

header img {
  height: 50px;
  width: auto;
}