@utkirbek: Opera Air is for mindfulness and calm, hence the more muted color palette. not a stark and over rated visual theme like dark.
there are plenty other browsers with tons of dark "edge-lord with bladerunner style background music" based themes. perhaps one of them (like stock Opera or Opera GX) would be a better fit for you.

The cat is fun and whimsically addition to Opera Air.
One suggestion would be to select the color of the cat (orange, tabby, black and so on).
I understand that the white one is more in line with the overall color palette of Opera Air so its no big deal.