freesewing/packages/css-theme/src/_theme-wrapper.scss

.theme-wrapper {
  margin: 0;
  padding: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.theme-wrapper.light {
  background: $fc-bg-light;
  color: $fc-bg-dark;
  .altbg {
    background: $fc-altbg-light;
  }
}

.theme-wrapper.dark {
  background: $fc-bg-dark;
  color: $fc-bg-light;
  .altbg {
    background: $fc-altbg-dark;
  }
}