html {
  position: fixed;
  width: 100%;
}

header {
  background-color: black;
  position: fixed;
  width: 100%;
  height: 4.5rem;
  padding-top: 2rem;
}

main {
  overflow-y: scroll;
  overflow-x: hidden;
  position: relative;
  top: 4.5rem;
  height: calc(100vh - 4.5rem);
}

.hidden {
  display: none !important;
}

.container {
  margin: 0 auto;
}

@media screen and (min-width: 500px) {
  .container {
    max-width: 800px;
  }

  header {
    height: 3.5rem;
    padding-top: 1rem;
  }

  main {
    top: 3.5rem;
    height: calc(100vh - 3.5rem);
    padding-left: 16px;
  }
}