Nit: the transitions don't add value and make the interactions feel inconsistent. I would recommend to remove them. If you want to keep them then they should be 200ms at most.

I can see how the _hover styles_ create inconsistent interactions (because they're based on hovering on the areas, while the labels use a nearest-point search). Not sure if removing the _transitions_ solves this.

The transition only happens while the cursor is inside at least one area. As soon as you move the cursor outside of all areas or over a dot the fills immediately reset. This is more noticeable with longer transition durations like the previous 600ms.

oh I see: it's because it wasn't set when not hovered. Is it better now?

Yup! But I'd still keep the transition durations below the threshold that I mentioned, because anything above will feel sluggish.

thanks for the feedback!