Very little if you're not a ux person.
Flex is where it's at, but have a general overview of both
Root7306255d@Wisecrack Like @SortOfTested, I would recommend knowing the basic box model, the positions, displays, floats, and definitely a beginning grasp of flex. Grid is nice, too. You should probably also know how to write media queries (responsiveness) and imports, but I wouldn’t focus on any more than basics there.
Unless you’re going for frontend, CSS questions should be minimal at best.
Wisecrack476554d@Root I dont have formal backend training (college), and have literally zero access to go that direction, and I heard frontend was easier to get the foot in the door, even though I probably know more about backend than frontend.
A lot of people hate frontend apparently, so people are always looking to move to backend and that means frontend positions should always be opening up.
Also I love UX.
I got into game design, and instead of making games, I just redesigned UIs over and over and never once got bored in the four years that I did it on the side.