Since implementing the dark mode I have been focusing more on the design of the site. Maybe it's just the darkness that brought all those little things into the daylight. Lighter themes might be more forgiving while darker overall is heavy enough on it's own that it requires more minimal design otherwise.
There is also a lot of balancing making everything work effortlessly between the light and the darkness. Less elements means less tinkering on how they look between these two. Keeping it simple I tried to reduce all the colours down to three (plus the highlight): dark, light and in-between. Dark and light are simply swapped when switching the theme while the other two remain the same. Simple and elegant!
The final colour of the site is green. No, you won't see it anywhere on the actual site. It's more on the ideal level: the carbon footprint of the site. After the latest changes the footprint is down by 15% (already down to 0,48g CO2 per page load) , but there is still a long way to reach my target. On the other hand this shouldn't be too hard. The site is still quite heavy on JavaScript despite having such a low amount of functionality. This is mainly due the Firebase and MDL frameworks which are quite bloated. But I'm confident I can cut the amount of code down substantially by moving more logic to the functions in the backend and using only the needed components from those frameworks instead of bringing in the whole bundle.