Customising Headline Theme Logo Size?!

Heeeey everyone,

I’m new to Ghost and putting together a website generally. I’ve been hacking away trying to get my logo the right size (mostly using code injection and increasing .gh-head-logo img {max-height: ???px;}) but when I preview on mobile it looks terrible.

Is there a way to make the logo fit “better”?

Website for reference…
https://www.data-viz.com/

Thanks!
Dan