Difficult to determine which card is active

I agree with P.B., this theme made perfect decisions on darkness and contrast control. Comfortable and stable. The original theme (by elibroftw) choosed black in tab background, but I like this theme's color selection, dark gray. I'm using (vanilla) Firefox with compact mode, and this fits perfectly.

I don't use Waterfox but this extension has the perfect darkness for my mac, it's not too dark for the text to be too hard to see and it's not light grey, it is perfect! I love it with Firefox Nightly.