Very good contrast, no stupid color choices, a little interesting without being distractingly busy, and it's easy to tell which tab is the active tab. This is a surprisingly rare combination of features in a Firefox theme, and this Blue Nebula Space theme is by far the best example I've found.

good

I love this theme! I have used it for over half a year now. Very cute and also great contrast as well so I can see the tabs and texts for each tab.

Beautiful!

amazing and updated

Hey, that's pretty good!

Clean, not hard on your eyes even in dark rooms. Kinda perfect so far! I'm gonna give "Blue Nebula (Variant 2)" a test also though.