body {
  padding: 0;
  margin: 0;
  background-color: grey;
}

.header {
  height: 3rem;
  background-color: aliceblue;
}

main {
  padding: 1rem;
}

.navigation {
  z-index: 100;
  position: absolute;
}

.navigation ul {
  width: 75vw;
  padding: 0;
  margin: 0;
  list-style: none;
  background-color: aquamarine;
  height: 100vh;
}

.navigation li a {
    padding: 1rem;
    border-bottom: solid 0.1rem;
    display: block;
    height: 100%;
}
.navigation li a:hover {
    background-color: blue;
}

details summary > * {
  display: inline;
}

details summary {
  list-style: none;
  cursor: pointer;
  padding: 1rem;
}

details summary::-webkit-details-marker {
  display: none;
}