body {
  display: grid;
  grid-template-columns: 1fr;
  grid-template-rows: 6rem 1fr;
  grid-column-gap: 0;
  grid-row-gap: 0;
  grid-template-areas: "header" "main";
}

header {
  grid-area: header;
  z-index: 2;
}

main {
  grid-area: main;
}