header {
/*  Made the header stay at the top  */
  position: sticky; /* 'fixed' can also work */

  /*  Tell it where to stick/fix to  */
  top: 0;
  left: 0;
  right: 0;
  
/*  Irrelevant styling  */
  background-color: teal;
  padding: 1rem 2rem;
}

.logo--big {
  /* Desired width when big */
  width: 140px;
  
  /* Make it a smooth transition */
  transition: width 0.2s ease-in-out;
}

.logo--small{
  /* Desired width when small */
  width: 50px;
  
  /* Make it a smooth transition */
  transition: width 0.2s ease-in-out;
}



/* Irrelevant styles */
body {
  padding: 0;
  margin:0;
  font-family: sans-serif;
}
#logo {
  fill: white;
}
.content {
  padding: 2rem;
  margin-top: 2rem;
  height: 200px;
}