Ever since I upgraded Firefox to 57, I was unable to find a worthwhile theme that wasn't too intrusive, easy for the eyes, can see at a glance what tab I look into and some pattern of dark blue squares or something similar. This is it.

Easy on the eyes! And like Blue and Black! Good job!

The best

First time going from standard theme. WOW! This pops.

Using the light bar and contrast to easily identify the current tab is brilliant.
This is theme is now part of my browser essentials for every new installation.

Tell you what I like about this theme? OK... Be specific? No problem... It's dark blue.✅ It's carbon fiber.✅ It's free.✅ I think that covers it... Well done random Firefox wallpaper maker person(s). One day you'll make something that people will actually spend real money on. Seriously! I wouldn't sh*t you...