We just pushed a change that will affect a small set of users who have enabled Dark Mode: in particular, Dark Mode’s going away.
Alas, we couldn’t find a nice middle that would confer the eye-saving benefits of editing on a dark background, but not place new requirements on notebook authors - like the need to design dark charts. We want Observable to be flexible and feel like a well-honed tool, but sometimes those things are in conflict - so in this case we want to devote time to making the default color scheme great instead of being split.
So - I hope folks understand the rationale behind this call. We’ll keep the dark mode setting around in the database, so that perhaps once we hire some élite designers, it will make a comeback.