:root {
  background: #f5f7fb;
  color-scheme: light;
}
:root[data-theme="dark"] {
  background: #000;
  color-scheme: dark;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    background: #000;
    color-scheme: dark;
  }
}