It's not a complex feature because most UIs have already been simplified and flattened into oblivion. If buttons and controls still had depth you might need two complete sets of assets. E.g. consider what implementing dark mode in iOS 6 might look like.
That's kind of my whole point. Dark mode features are a symptom of UIs that no longer communicate anything significant with color and shade so just changing color with CSS tweaks doesn't break them.
That's kind of my whole point. Dark mode features are a symptom of UIs that no longer communicate anything significant with color and shade so just changing color with CSS tweaks doesn't break them.