header {
  display: flex;
  width: 100%;
  box-sizing: border-box;
  align-items: center;
  justify-content: center;
  position: fixed;
  bottom: 0;
  left: 0;
  z-index: 100;
  background: var(--header-bg-color);
  backdrop-filter: blur(0.25em);
  box-shadow: var(--header-shadow);

  nav {
    display: flex;
    gap: 1em;
  }

  form {
    width: auto;
    max-width: inherit;
  }

  a, button {
    font: inherit;
    font-weight: bold;
    cursor: pointer;
    color: var(--button-fg-color);

    display: flex;
    box-sizing: border-box;
    align-items: center;
    justify-content: center;
    /* A phone reaches this bar with a thumb, so the label alone is not the
       target — the whole 4em band is. */
    height: 4em;
    padding: 0 1em;
    min-width: 2em;
    background: transparent;
    border: none;

    &:hover {
      background: var(--header-link-hover-color);
      color: var(--button-fg-color);
      text-decoration: none;
    }
  }

  button {
    margin-right: 0;
  }
}

@media screen and (min-width: 36em) {
  header {
    position: relative;
    background: none;
    backdrop-filter: none;
    box-shadow: none;
    padding: 0 1em;
  }

  header :is(a, button) {
    height: auto;
    padding: 0.5em 0;
    color: var(--link-color);

    &:hover {
      background: none;
      color: var(--link-hover-color);
      text-decoration: underline;
    }
  }
}