body{
  margin: 0;
}
#wrapper{
  display: grid;
  gap: 12px;
}
#wrapper > *{
  padding: 1rem;
  font-size: 1.2rem;
  color: royalblue;
  background-color: lightblue;
}
header{
  position: relative;
  min-width: 80px;
}
nav ul{
  padding-left: 0.5em;
}
nav li{
  display: inline-block;
  margin-right: 1em;
  color: #333;
}
#menu{
  position: absolute;
  top: 0;
  right: 0;
  padding: 0 1rem;
  height: 64px;
  line-height: 64px;
  color: #333;
  cursor: pointer;
}
main div{
  margin: 1em;
  padding: 1em;
  height: 67vh;
  color: #333;
  background-color: yellow;
}
footer{
  height: 20px;
}
@media (max-width: 768px){
  nav{
    display: none;
  }
  #menu:hover + nav{
    display: inherit;
    text-align: right;
  }
  #menu:hover + nav li{
    display: block;
    padding: 0.6em;
  }
}

@media (min-width: 769px){
  #menu{
    display: none;
  }
  #wrapper{
    grid-template-columns: 200px 1fr;
  }
  header{
    grid-column: 1 / -1;
  }
  footer{
    grid-column: 1 / -1;
  }
}