See https://developer.mozilla.org/en-US/docs/Web/CSS/:root#declaring_global_css_variables https://developer.mozilla.org/en-US/docs/Web/CSS/:root#decla.... With

See https://developer.mozilla.org/en-US/docs/Web/CSS/:root#declaring_global_css_variables https://developer.mozilla.org/en-US/docs/Web/CSS/:root#decla.... With :root, you can write css variables that can be accessed by any other element on the page (?). So to implement a light and dark theme, you could have something like `@media (prefers-color-scheme: light){ :root { --bg-color: #FFF; }`, and then have the body element use that via `body { background: var(--bg-color); }`.